RESUMEN
Gram-negative bacteria produce chaperone-usher pathway pili, which are extracellular protein fibers tipped with an adhesive protein that binds to a receptor with stereochemical specificity to determine host and tissue tropism. The outer-membrane usher protein, together with a periplasmic chaperone, assembles thousands of pilin subunits into a highly ordered pilus fiber. The tip adhesin in complex with its cognate chaperone activates the usher to allow extrusion across the outer membrane. The structural requirements to translocate the adhesin through the usher pore from the periplasm to the extracellular space remains incompletely understood. Here, we present a cryoelectron microscopy structure of a quaternary tip complex in the type 1 pilus system from Escherichia coli, which consists of the usher FimD, chaperone FimC, adhesin FimH, and the tip adapter FimF. In this structure, the usher FimD is caught in the act of secreting its cognate adhesin FimH. Comparison with previous structures depicting the adhesin either first entering or having completely exited the usher pore reveals remarkable structural plasticity of the two-domain adhesin during translocation. Moreover, a piliation assay demonstrated that the structural plasticity, enabled by a flexible linker between the two domains, is a prerequisite for adhesin translocation through the usher pore and thus pilus biogenesis. Overall, this study provides molecular details of adhesin translocation across the outer membrane and elucidates a unique conformational state adopted by the adhesin during stepwise secretion through the usher pore. This study elucidates fundamental aspects of FimH and usher dynamics critical in urinary tract infections and is leading to antibiotic-sparing therapeutics.
Asunto(s)
Adhesinas de Escherichia coli , Microscopía por Crioelectrón , Proteínas de Escherichia coli , Escherichia coli , Proteínas Fimbrias , Fimbrias Bacterianas , Proteínas Fimbrias/metabolismo , Proteínas Fimbrias/química , Fimbrias Bacterianas/metabolismo , Adhesinas de Escherichia coli/metabolismo , Adhesinas de Escherichia coli/química , Proteínas de Escherichia coli/metabolismo , Proteínas de Escherichia coli/química , Escherichia coli/metabolismo , Chaperonas Moleculares/metabolismo , Chaperonas Moleculares/química , Modelos Moleculares , Proteínas de la Membrana Bacteriana Externa/metabolismo , Proteínas de la Membrana Bacteriana Externa/químicaRESUMEN
Klebsiella pneumoniae is an important pathogen causing difficult-to-treat urinary tract infections (UTIs). Over 1.5 million women per year suffer from recurrent UTI, reducing quality of life and causing substantial morbidity and mortality, especially in the hospital setting. Uropathogenic E. coli (UPEC) is the most prevalent cause of UTI. Like UPEC, K. pneumoniae relies on type 1 pili, tipped with the mannose-binding adhesin FimH, to cause cystitis. However, K. pneumoniae FimH is a poor binder of mannose, despite a mannose-binding pocket identical to UPEC FimH. FimH is composed of two domains that are in an equilibrium between tense (low-affinity) and relaxed (high-affinity) conformations. Substantial interdomain interactions in the tense conformation yield a low-affinity, deformed mannose-binding pocket, while domain-domain interactions are broken in the relaxed state, resulting in a high-affinity binding pocket. Using crystallography, we identified the structural basis by which domain-domain interactions direct the conformational equilibrium of K. pneumoniae FimH, which is strongly shifted toward the low-affinity tense state. Removal of the pilin domain restores mannose binding to the lectin domain, thus showing that poor mannose binding by K. pneumoniae FimH is not an inherent feature of the mannose-binding pocket. Phylogenetic analyses of K. pneumoniae genomes found that FimH sequences are highly conserved. However, we surveyed a collection of K. pneumoniae isolates from patients with long-term indwelling catheters and identified isolates that possessed relaxed higher-binding FimH variants, which increased K. pneumoniae fitness in bladder infection models, suggesting that long-term residence within the urinary tract may select for higher-binding FimH variants.
Asunto(s)
Proteínas Fimbrias , Klebsiella pneumoniae , Manosa , Infecciones Urinarias , Klebsiella pneumoniae/metabolismo , Klebsiella pneumoniae/genética , Proteínas Fimbrias/metabolismo , Proteínas Fimbrias/química , Proteínas Fimbrias/genética , Infecciones Urinarias/microbiología , Manosa/metabolismo , Humanos , Conformación Proteica , Adhesinas de Escherichia coli/metabolismo , Adhesinas de Escherichia coli/química , Adhesinas de Escherichia coli/genética , Sitios de Unión , Dominios Proteicos , Infecciones por Klebsiella/microbiología , Cristalografía por Rayos X , Modelos Moleculares , Adhesinas Bacterianas/metabolismo , Adhesinas Bacterianas/química , Adhesinas Bacterianas/genética , Unión Proteica , Femenino , Fimbrias Bacterianas/metabolismoRESUMEN
The adhesin FimH is expressed by commensal Escherichia coli and is implicated in urinary tract infections, where it mediates adhesion to mannosylated glycoproteins on urinary and intestinal epithelial cells in the presence of a high-shear fluid environment. The FimH-mannose bond exhibits catch behavior in which bond lifetime increases with force, because tensile force induces a transition in FimH from a compact native to an elongated activated conformation with a higher affinity to mannose. However, the lifetime of the activated state of FimH has not been measured under force. Here we apply multiplexed magnetic tweezers to apply a preload force to activate FimH bonds with yeast mannan, then we measure the lifetime of these activated bonds under a wide range of forces above and below the preload force. A higher fraction of FimH-mannan bonds were activated above than below a critical preload force, confirming the FimH catch bond behavior. Once activated, FimH detached from mannose with multi-state kinetics, suggesting the existence of two bound states with a 20-fold difference in dissociation rates. The average lifetime of activated FimH-mannose bonds was 1000 to 10,000 s at forces of 30-70 pN. Structural explanations of the two bound states and the high force resistance provide insights into structural mechanisms for long-lived, force-resistant biomolecular interactions.
Asunto(s)
Adhesinas de Escherichia coli , Proteínas Fimbrias , Manosa , Adhesinas de Escherichia coli/química , Adhesinas de Escherichia coli/metabolismo , Manosa/química , Manosa/metabolismo , Proteínas Fimbrias/química , Proteínas Fimbrias/metabolismo , Unión Proteica , Mananos/química , Mananos/metabolismo , Cinética , Factores de Tiempo , Fenómenos BiomecánicosRESUMEN
Antigen 43 (Ag43) proteins, found on the outer membrane of Escherichia coli, are ß-sheets that fold into a unique cylindrical structure known as a ß-barrel. There are several known structural similarities between bacterial Ag43 autotransporters and physical components; however, the factors that stabilize the barrel and the mechanism for Ag43 passenger domainmediated translocation across the pore of the ß-barrel remain unclear. In this study, we analyzed Ag43ß-enhanced green fluorescent protein chimeric variants to provide new insights into the autotransporter Ag43ß-barrel assembly, focusing on the impact of the α-helical linker domain. Among the chimeric variants, Ag43ß700 showed the highest surface display, which was confirmed through extracellular protease digestion, flow cytometry, and an evaluation of outer membrane vesicles (OMVs). The Ag43ß700 module offered reliable information on stable barrel folding and chimera expression at the exterior of the OMVs. [BMB Reports 2024; 57(8): 369-374].
Asunto(s)
Membrana Externa Bacteriana , Escherichia coli , Proteínas Fluorescentes Verdes , Adhesinas de Escherichia coli/metabolismo , Adhesinas de Escherichia coli/química , Adhesinas de Escherichia coli/genética , Membrana Externa Bacteriana/metabolismo , Proteínas de la Membrana Bacteriana Externa/metabolismo , Proteínas de la Membrana Bacteriana Externa/química , Escherichia coli/metabolismo , Proteínas de Escherichia coli/metabolismo , Proteínas de Escherichia coli/química , Proteínas Fluorescentes Verdes/metabolismo , Proteínas Fluorescentes Verdes/genética , Pliegue de ProteínaRESUMEN
FmlH, a bacterial adhesin of uropathogenic Escherichia coli (UPEC), has been shown to provide a fitness advantage in colonizing the bladder during chronic urinary tract infections (UTIs). Previously reported ortho-biphenyl glycosides based on ßGal and ßGalNAc have excellent binding affinity to FmlH and potently block binding to its natural carbohydrate receptor, but they lack oral bioavailability. In this paper, we outline studies where we have optimized compounds for improved pharmacokinetics, leading to the discovery of novel analogues with good oral bioavailability. We synthesized galactosides with the anomeric O-linker replaced with more stable S- and C-linked linkers. We also investigated modifications to the GalNAc sugar and modifications to the biphenyl aglycone. We identified GalNAc 69 with an IC50 of 0.19 µM against FmlH and 53% oral bioavailability in mice. We also obtained a FimlH-bound X-ray structure of lead compound 69 (AM4085) which has potential as a new antivirulence therapeutic for UTIs.
Asunto(s)
Infecciones por Escherichia coli , Infecciones Urinarias , Escherichia coli Uropatógena , Ratones , Animales , Lectinas , Adhesinas de Escherichia coli/química , Infecciones Urinarias/tratamiento farmacológico , Compuestos de Bifenilo/química , Escherichia coli Uropatógena/metabolismo , Infecciones por Escherichia coli/tratamiento farmacológicoRESUMEN
Autotransporters constitute a large family of natural proteins that are essential for delivering many types of proteins and peptides across the outer membrane in Gram-negative bacteria. In biotechnology, autotransporters have been explored for display of recombinant proteins and peptides on the surface of Escherichia coli and have potential as tools for directed evolution of affinity proteins. Here, we investigate conditions for AIDA-I autotransporter-mediated display of recombinant proteins. A new expression vector was designed and engineered for this purpose, and a panel of proteins from different affinity-protein classes were subcloned to the vector, followed by evaluation of expression, surface display and functionality. Surface expression was explored in ten different E. coli strains together with assessment of transformation efficiencies. Furthermore, the most promising strain and expression vector combination was used in mock library selections for evaluation of magnetic-assisted cell sortings (MACS). The results demonstrated dramatically different performances depending on the type of affinity protein and choice of E. coli strain. The optimized MACS protocol showed efficient enrichment, and thus potential for the new AIDA-I display system to be used in methods for directed evolution of affinity proteins.
Asunto(s)
Proteínas de Escherichia coli , Escherichia coli , Escherichia coli/genética , Escherichia coli/metabolismo , Adhesinas de Escherichia coli/química , Sistemas de Secreción Tipo V/metabolismo , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Péptidos/metabolismoRESUMEN
The bacterial adhesin FimH is a model for the study of protein allostery because its structure has been resolved in multiple configurations, including the active and the inactive state. FimH consists of a pilin domain (PD) that anchors it to the rest of the fimbria and an allosterically regulated lectin domain (LD) that binds mannose on the surface of infected cells. Under normal conditions, the two domains are docked to each other and LD binds mannose weakly. However, in the presence of tensile force generated by shear the domains separate and conformational changes propagate across LD resulting in a stronger bond to mannose. Recently, the crystallographic structure of a variant of FimH has been resolved, called FimH FocH , where PD contains 10 mutations near the inter-domain interface. Although the X-ray structures of FimH and FimH FocH are almost identical, experimental evidence shows that FimH FocH is activated even in the absence of shear. Here, molecular dynamics simulations combined with the Jarzynski equality were used to investigate the discrepancy between the crystallographic structures and the functional assays. The results indicate that the free energy barrier of the unbinding process between LD and PD is drastically reduced in FimH FocH . Rupture of inter-domain hydrogen bonds involving R166 constitutes a rate limiting step of the domain separation process and occurs more readily in FimH FocH than FimH. In conclusion, the mutations in FimH FocH shift the equilibrium toward an equal occupancy of bound and unbound states for LD and PD by reducing a rate limiting step.
Asunto(s)
Manosa , Simulación de Dinámica Molecular , Manosa/química , Regulación Alostérica , Adhesinas de Escherichia coli/química , Escherichia coli/genética , Proteínas Fimbrias/química , Lectinas/metabolismoRESUMEN
BACKGROUND: Avian Escherichia coli (E.coli) type 1 fimbriae adhere to avian tracheal epithelial cells through the FimH protein. However, the adhesion-related antigen is still unknown. The purpose of this study was to analyze the antigenicity of the type 1 fimbrial FimH protein of wild-type avian E. coli, screen antigen epitopes, and prepare monoclonal antibodies (mAbs) that can block the adhesion of avian E. coli. RESULTS: In this study, the nucleic acid homologies of MG2 (O11), TS12 (O18), and YR5 (O78) with K12 were 97.7%, 99.6%, and 97.7%, respectively, and the amino acid sequence similarity reached 98.7%, 99.3%, and 98.0%, respectively. The epitopes and hydrophilicities of the FimH proteins of these three strains were similar. The more obvious lectin domain epitopes were located at FimH protein positions 111-124 and 154-162. The mAbs 7C2 and 7D8 against these two epitopes were prepared. An adhesion inhibition test showed that 7C2 and 7D8 blocked bacterial adhesion to avian tracheal epithelial cells. The mAb 7C2 against the 111-124 epitope inhibited O78 strain adhesion by 93%, and the mAb 7D8 against the 154-162 epitope inhibited O78 strain adhesion by 49%, indicating that these two epitopes are closely related to the adhesion of type 1 fimbriae. However, only the 111-124 epitope-recognizing mAb 7C2 inhibited bacterial agglutination of erythrocytes, indicating that host cell receptor binding and erythrocyte agglutination are not mediated by the same spatial locations within the FimH protein. CONCLUSIONS: The results demonstrate that the mAbs 7C2 and 7D8 against FimH protein positions 111-124 and 154-162 could inhibit the adhesion of E.coli to the chicken trachea.
Asunto(s)
Escherichia coli , Proteínas Fimbrias , Animales , Escherichia coli/genética , Proteínas Fimbrias/genética , Epítopos/metabolismo , Adhesinas de Escherichia coli/genética , Adhesinas de Escherichia coli/química , Aglutininas/metabolismo , Adhesión BacterianaRESUMEN
The nature of alpha-D-mannose-natural aldohexose sugar, C-2 glucose epimer, whose intended use is for preventing urinary tract infections-in the interaction with E. coli is addressed in order to drive the issue of its regulatory classification as a medicinal product or medical device. PRISMA systematic review approach was applied; Delphi Panel method was used to target consensus on statements retrieved from evidence. Based on regulatory definitions and research evidence, the mechanism of D-mannose does not involve a metabolic or immunological action while there is uncertainty regarding the pharmacological action. Specific interaction between the product and the bacteria within the body occurs, but its nature is inert: it does not induce a direct response activating or inhibiting body processes. Moreover, the action of D-mannose takes place, even if inside the bladder, outside the epithelium on bacteria that have not yet invaded the urothelial tissue. Therefore, its mechanism of action is not directed to host structures but to structures (bacteria) external to the host's tissues. On the basis of current regulation, the uncertainty as regard a pharmacological action of alpha-D-mannose makes possible its medical device classification: new regulations and legal judgments can add further considerations. From a pharmacological perspective, research is driven versus synthetic mannosides: no further considerations are expected on alpha-D-mannose.
Asunto(s)
Escherichia coli , Manosa , Adhesinas de Escherichia coli/química , Adhesinas de Escherichia coli/metabolismo , Consenso , Escherichia coli/química , Escherichia coli/metabolismo , Proteínas Fimbrias/química , Proteínas Fimbrias/metabolismo , Manosa/química , Manosa/metabolismo , Revisiones Sistemáticas como AsuntoRESUMEN
The bacterial fimbrial adhesin FimH is a remarkable and well-studied catch-bond protein found at the tip of E. coli type 1 pili, which allows pathogenic strains involved in urinary tract infections to bind high-mannose glycans exposed on human epithelia. The catch-bond behavior of FimH, where the strength of the interaction increases when a force is applied to separate the two partners, enables the bacteria to resist clearance when they are subjected to shear forces induced by urine flow. Two decades of experimental studies performed at the single-molecule level, as well as x-ray crystallography and modeling studies, have led to a consensus picture whereby force separates the binding domain from an inhibitor domain, effectively triggering an allosteric conformational change in the former. This force-induced allostery is thought to be responsible for an increased binding affinity at the core of the catch-bond mechanism. However, some important questions remain, the most challenging one being that the crystal structures corresponding to these two allosteric states show almost superimposable binding site geometries, which questions the molecular origin for the large difference in affinity. Using molecular dynamics with a combination of enhanced-sampling techniques, we demonstrate that the static picture provided by the crystal structures conceals a variety of binding site conformations that have a key impact on the apparent affinity. Crucially, the respective populations in each of these conformations are very different between the two allosteric states of the binding domain, which can then be related to experimental affinity measurements. We also evidence a previously unappreciated but important effect: in addition to the well-established role of the force as an allosteric regulator via domain separation, application of force tends to directly favor the high-affinity binding site conformations. We hypothesize that this additional "local" catch-bond effect could delay unbinding between the bacteria and the host cell before the "global" allosteric transition occurs, as well as stabilizing the complex even more once in the high-affinity allosteric state.
Asunto(s)
Escherichia coli , Proteínas Fimbrias , Humanos , Escherichia coli/metabolismo , Proteínas Fimbrias/metabolismo , Adhesinas de Escherichia coli/química , Adhesinas de Escherichia coli/metabolismo , Adhesión Bacteriana/fisiología , Sitios de Unión , Unión ProteicaRESUMEN
The FimH type-1 fimbrial adhesin allows pathogenic Escherichia coli to adhere to glycoproteins in the epithelial linings of human bladder and intestinal tract, by using multiple fimbriae simultaneously. Pauci- and high-mannose type N-glycans are natural FimH receptors on those glycoproteins. Oligomannose-3 and oligomannose-5 bind with the highest affinity to FimH by using the same Manα1,3Man branch. Oligomannose-6 is generated from oligomannose-5 in the next step of the biogenesis of high-mannose N-glycans, by the transfer of a mannose in α1,2-linkage onto this branch. Using serial crystallography and by measuring the kinetics of binding, we demonstrate that shielding the high-affinity epitope drives the binding of multiple FimH molecules. First, we profiled FimH glycan binding on a microarray containing paucimannosidic N-glycans and in a FimH LEctPROFILE assay. To make the transition to oligomannose-6, we measured the kinetics of FimH binding using paucimannosidic N-glycans, glycoproteins and all four α-dimannosides conjugated to bovine serum albumin. Equimolar mixed interfaces of the dimannosides present in oligomannose-6 and molecular dynamics simulations suggest a positive cooperativity in the bivalent binding of Manα1,3Manα1 and Manα1,6Manα1 dimannosides. The binding of core α1,6-fucosylated oligomannose-3 in cocrystals of FimH is monovalent but interestingly the GlcNAc1-Fuc moiety retains highly flexibility. In cocrystals with oligomannose-6, two FimH bacterial adhesins bind the Manα1,3Manα1 and Manα1,6Manα1 endings of the second trimannose core (A-4'-B). This cooperative switch towards bivalent binding appears sustainable beyond a molar excess of oligomannose-6. Our findings provide important novel structural insights for the design of multivalent FimH antagonists that bind with positive cooperativity.
Asunto(s)
Adhesinas de Escherichia coli , Receptor de Manosa , Modelos Moleculares , Humanos , Adhesinas de Escherichia coli/química , Adhesinas de Escherichia coli/metabolismo , Adhesión Bacteriana , Escherichia coli/metabolismo , Glicoproteínas/metabolismo , Manosa/metabolismo , Receptor de Manosa/química , Receptor de Manosa/metabolismo , Polisacáridos/metabolismo , Unión Proteica , Estructura Cuaternaria de Proteína , Simulación del Acoplamiento MolecularRESUMEN
The increase in multidrug-resistant pathogens in urinary tract infections (UTIs) among communities and hospitals threatens our ability to treat these common pathogens. Uropathogenic Escherichia coli (UPEC) strains are the most frequent uropathies linked to the development of UTIs. This work aims to introduce bioactive natural products via virtual screening of small molecules from a public database to prevent biofilm formation by inhibiting FimH, a type 1 fimbriae that plays a crucial role in UPEC pathogenicity. A total of 30926 small molecules from the NPASS database were subjected to screening via molecular docking. Followed by performing in silico ADME studies, seven molecules showed promising docking results ranging from -6.8 to -8.7 kcal/mol. As a result of the docking score findings, 100 ns Molecular dynamics (MD) simulations were performed. Based on MM-PBSA analysis, NPC313334 ligand showed high binding affinity -42 and stability with the binding pocket of FimH protein during molecular dynamic simulations. DFT calculations were also performed on the ligands to calculate the HOMO-LUMO energies of the compounds in order to an idea about their structure and reactivity. This research suggests that NPC313334 may be a possible antibacterial drug candidate that targets FimH to reduce the number of UPEC-related urinary tract infections.Communicated by Ramaswamy H. Sarma.
Asunto(s)
Adhesinas de Escherichia coli , Infecciones Urinarias , Humanos , Adhesinas de Escherichia coli/química , Adhesinas de Escherichia coli/metabolismo , Proteínas Fimbrias/química , Proteínas Fimbrias/metabolismo , Proteínas Fimbrias/uso terapéutico , Simulación del Acoplamiento Molecular , Lectinas , Antibacterianos/farmacología , Infecciones Urinarias/tratamiento farmacológico , Infecciones Urinarias/microbiología , Infecciones Urinarias/prevención & controlRESUMEN
A key attribute of persistent or recurring bacterial infections is the ability of the pathogen to evade the host's immune response. Many Enterobacteriaceae express type 1 pili, a pre-adapted virulence trait, to invade host epithelial cells and establish persistent infections. However, the molecular mechanisms and strategies by which bacteria actively circumvent the immune response of the host remain poorly understood. Here, we identified CD14, the major co-receptor for lipopolysaccharide detection, on mouse dendritic cells (DCs) as a binding partner of FimH, the protein located at the tip of the type 1 pilus of Escherichia coli. The FimH amino acids involved in CD14 binding are highly conserved across pathogenic and non-pathogenic strains. Binding of the pathogenic strain CFT073 to CD14 reduced DC migration by overactivation of integrins and blunted expression of co-stimulatory molecules by overactivating the NFAT (nuclear factor of activated T-cells) pathway, both rate-limiting factors of T cell activation. This response was binary at the single-cell level, but averaged in larger populations exposed to both piliated and non-piliated pathogens, presumably via the exchange of immunomodulatory cytokines. While defining an active molecular mechanism of immune evasion by pathogens, the interaction between FimH and CD14 represents a potential target to interfere with persistent and recurrent infections, such as urinary tract infections or Crohn's disease.
Asunto(s)
Infecciones por Escherichia coli , Escherichia coli Uropatógena , Adhesinas de Escherichia coli/química , Adhesinas de Escherichia coli/genética , Adhesinas de Escherichia coli/metabolismo , Animales , Infecciones por Escherichia coli/microbiología , Proteínas Fimbrias/metabolismo , Fimbrias Bacterianas/metabolismo , Inmunidad , Ratones , Escherichia coli Uropatógena/fisiologíaRESUMEN
Allosteric proteins transition between 'inactive' and 'active' states. In general, such proteins assume distinct conformational states at the level of secondary, tertiary and/or quaternary structure. Different conformers of an allosteric protein can be antigenically dissimilar and induce antibodies with a highly distinctive specificities and neutralizing functional effects. Here we summarize studies on various functional types of monoclonal antibodies obtained against different allosteric conformers of the mannose-specific bacterial adhesin FimH - the most common cell attachment protein of Escherichia coli and other enterobacterial pathogens. Included are types of antibodies that activate the FimH function via interaction with ligand-induced binding sites or by wedging between domains as well as antibodies that inhibit FimH through orthosteric, parasteric, or novel dynasteric mechanisms. Understanding the molecular mechanism of antibody action against allosteric proteins provides insights on how to design antibodies with a desired functional effect, including those with neutralizing activity against bacterial and viral cell attachment proteins.
Asunto(s)
Adhesinas de Escherichia coli , Anticuerpos Neutralizantes , Proteínas Fimbrias , Adhesinas de Escherichia coli/química , Adhesinas de Escherichia coli/inmunología , Regulación Alostérica , Anticuerpos Neutralizantes/química , Anticuerpos Neutralizantes/inmunología , Proteínas Fimbrias/química , Proteínas Fimbrias/inmunología , Conformación ProteicaRESUMEN
The FimH protein of Escherichia coli is a model two-domain adhesin that is able to mediate an allosteric catch bond mechanism of bacterial cell attachment, where the mannose-binding lectin domain switches from an 'inactive' conformation with fast binding to mannose to an 'active' conformation with slow detachment from mannose. Because mechanical tensile force favors separation of the domains and, thus, FimH activation, it has been thought that the catch bonds can only be manifested in a fluidic shear-dependent mode of adhesion. Here, we used recombinant FimH variants with a weakened inter-domain interaction and show that a fast and sustained allosteric activation of FimH can also occur under static, non-shear conditions. Moreover, it appears that lectin domain conformational activation happens intrinsically at a constant rate, independently from its ability to interact with the pilin domain or mannose. However, the latter two factors control the rate of FimH deactivation. Thus, the allosteric catch bond mechanism can be a much broader phenomenon involved in both fast and strong cell-pathogen attachments under a broad range of hydrodynamic conditions. This concept that allostery can enable more effective receptor-ligand interactions is fundamentally different from the conventional wisdom that allostery provides a mechanism to turn binding off under specific conditions.
Asunto(s)
Adhesinas de Escherichia coli , Adhesión Bacteriana , Escherichia coli , Proteínas Fimbrias , Adhesinas de Escherichia coli/química , Adhesinas de Escherichia coli/genética , Adhesinas de Escherichia coli/fisiología , Regulación Alostérica , Adhesión Bacteriana/fisiología , Escherichia coli/fisiología , Proteínas Fimbrias/química , Proteínas Fimbrias/genética , Manosa/metabolismo , Dominios Proteicos , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Resistencia al CorteRESUMEN
The formation of aggregates and biofilms enhances bacterial colonisation and infection progression by affording protection from antibiotics and host immune factors. Despite these advantages there is a trade-off, whereby bacterial dissemination is reduced. As such, biofilm development needs to be controlled to suit adaptation to different environments. Here we investigate members from one of largest groups of bacterial adhesins, the autotransporters, for their critical role in the assembly of bacterial aggregates and biofilms. We describe the structural and functional characterisation of autotransporter Ag43 variants from different Escherichia coli pathotypes. We show that specific interactions between amino acids on the contacting interfaces of adjacent Ag43 proteins drives a common mode of trans-association that leads to cell clumping. Furthermore, subtle variation of these interactions alters aggregation kinetics and the degree of compacting within cell clusters. Together, our structure-function investigation reveals an underlying molecular basis for variations in the density of bacterial communities.
Asunto(s)
Adhesinas de Escherichia coli , Proteínas de Escherichia coli , Adhesinas de Escherichia coli/química , Adhesión Bacteriana , Biopelículas , Escherichia coli/genética , Escherichia coli/metabolismo , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismoRESUMEN
Antigen 43 is a surface-displayed autotransporter protein that mediates bacterial self-association and pathogenicity. The quality control factors that facilitate Ag43 crossing the periplasm and inserting into the outer membrane remain enigmatic, mostly because Ag43 is phase variable and associated with heterologous phenotypes, which obscures the mutational effects of potential quality control factors. Here, we describe a screening method that allowed us to isolate a subpopulation of Escherichia coli that consistently displays an Ag43-mediated autoaggregation phenotype. Based on this subpopulation, we analyzed how disruptions of known periplasmic chaperones affect Ag43 biogenesis. We found that only the disruption of surA reduced Ag43 levels and abolished the autoaggregation phenotype of cells, but surA disruption did not affect the phase-variable expression of agn43. Using purified proteins, we showed that SurA effectively protected the ß-barrel domain of Ag43 from aggregation. In contrast, the previously reported Ag43 biogenesis factor OsmY showed weak chaperoning effects on Ag43 only in the absence of SurA. Our results shed light on the roles of different periplasmic chaperones in Ag43 biogenesis and provide a methodology applicable to the study of other phase-variable proteins.
Asunto(s)
Adhesinas de Escherichia coli/metabolismo , Escherichia coli/metabolismo , Chaperonas Moleculares/metabolismo , Periplasma/metabolismo , Sistemas de Secreción Tipo V/metabolismo , Adhesinas de Escherichia coli/química , Proteínas Portadoras/metabolismo , Proteínas de Escherichia coli/metabolismo , Isomerasa de Peptidilprolil/metabolismo , Fenotipo , Estructura Secundaria de ProteínaRESUMEN
MonteCarbo is an open-source software to construct simple 5-, 6-, and 7-membered ring multifunctionalized monosaccharides and nucleobases and dock them into the active site of carbohydrate-active enzymes. The core bash script executes simple orders to generate the Z-matrix of the neutral molecule of interest. After that, a Fortran90 code based on a pseudo-random number generator (Monte Carlo method) is executed to assign dihedral angles to the different rotamers present in the structure (ring and rotating functional groups). The program also has a generalized internal coordinates (GIC) implementation of the Cremer and Pople puckering coordinates ring. Once the structures are generated and optimized, a second code is ready to execute in serial the docking of multiple conformers in the active site of a wide family of enzymes.
Asunto(s)
Adhesinas de Escherichia coli/química , Carbohidratos/química , Proteínas Fimbrias/química , Simulación del Acoplamiento Molecular , Monosacáridos/química , Programas Informáticos , Adhesinas de Escherichia coli/metabolismo , Proteínas Fimbrias/metabolismo , Método de MontecarloRESUMEN
Escherichia coli express adhesion pili that mediate attachment to host cell surfaces and are exposed to body fluids in the urinary and gastrointestinal tracts. Pilin subunits are organized into helical polymers, with a tip adhesin for specific host binding. Pili can elastically unwind when exposed to fluid flow forces, reducing the adhesin load, thereby facilitating sustained attachment. Here we investigate biophysical and structural differences of pili commonly expressed on bacteria that inhabit the urinary and intestinal tracts. Optical tweezers measurements reveal that class 1a pili of uropathogenic E. coli (UPEC), as well as class 1b of enterotoxigenic E. coli (ETEC), undergo an additional conformational change beyond pilus unwinding, providing significantly more elasticity to their structure than ETEC class 5 pili. Examining structural and steered molecular dynamics simulation data, we find that this difference in class 1 pili subunit behavior originates from an α-helical motif that can unfold when exposed to force. A disulfide bond cross-linking ß-strands in class 1 pili stabilizes subunits, allowing them to tolerate higher forces than class 5 pili that lack this covalent bond. We suggest that these extra contributions to pilus resiliency are relevant for the UPEC niche, since resident bacteria are exposed to stronger, more transient drag forces compared to those experienced by ETEC bacteria in the mucosa of the intestinal tract. Interestingly, class 1b ETEC pili include the same structural features seen in UPEC pili, while requiring lower unwinding forces that are more similar to those of class 5 ETEC pili.
Asunto(s)
Adhesinas de Escherichia coli/química , Escherichia coli Enterotoxigénica/ultraestructura , Proteínas Fimbrias/química , Fimbrias Bacterianas/ultraestructura , Escherichia coli Uropatógena/ultraestructura , Adhesinas de Escherichia coli/genética , Adhesinas de Escherichia coli/metabolismo , Adhesión Bacteriana , Sitios de Unión , Fenómenos Biomecánicos , Cisteína/química , Cisteína/metabolismo , Disulfuros/química , Disulfuros/metabolismo , Escherichia coli Enterotoxigénica/genética , Escherichia coli Enterotoxigénica/metabolismo , Proteínas Fimbrias/genética , Proteínas Fimbrias/metabolismo , Fimbrias Bacterianas/genética , Fimbrias Bacterianas/metabolismo , Expresión Génica , Cinética , Simulación de Dinámica Molecular , Pinzas Ópticas , Unión Proteica , Conformación Proteica en Hélice alfa , Conformación Proteica en Lámina beta , Dominios y Motivos de Interacción de Proteínas , Estructura Terciaria de Proteína , Subunidades de Proteína/química , Subunidades de Proteína/genética , Subunidades de Proteína/metabolismo , Termodinámica , Escherichia coli Uropatógena/genética , Escherichia coli Uropatógena/metabolismoRESUMEN
The Food and Drug Administration (FDA) approved a new class of anti-diabetic medication (a sodium-glucose co-transporter 2 (SGLT2) inhibitor) in 2013. However, SGLT2 inhibitor drugs are under evaluation due to their associative side effects, such as urinary tract and genital infection, urinary discomfort, diabetic ketosis, and kidney problems. Even clinicians have difficulty in recommending it to diabetic patients due to the increased probability of urinary tract infection. In our study, we selected natural SGLT2 inhibitors, namely acerogenin B, formononetin, (-)-kurarinone, (+)-pteryxin, and quinidine, to explore their potential against an emerging uropathogenic bacterial therapeutic target, i.e., FimH. FimH plays a critical role in the colonization of uropathogenic bacteria on the urinary tract surface. Thus, FimH antagonists show promising effects against uropathogenic bacterial strains via their targeting of FimH's adherence mechanism with less chance of resistance. The molecular docking results showed that, among natural SGLT2 inhibitors, formononetin, (+)-pteryxin, and quinidine have a strong interaction with FimH proteins, with binding energy (∆G) and inhibition constant (ki) values of -5.65 kcal/mol and 71.95 µM, -5.50 kcal/mol and 92.97 µM, and -5.70 kcal/mol and 66.40 µM, respectively. These interactions were better than those of the positive control heptyl α-d-mannopyranoside and far better than those of the SGLT2 inhibitor drug canagliflozin. Furthermore, a 50 ns molecular dynamics simulation was conducted to optimize the interaction, and the resulting complexes were found to be stable. Physicochemical property assessments predicted little toxicity and good drug-likeness properties for these three compounds. Therefore, formononetin, (+)-pteryxin, and quinidine can be proposed as promising SGLT2 inhibitors drugs, with add-on FimH inhibition potential that might reduce the probability of uropathogenic side effects.