RESUMO
The potentiation of antibiotics is a promising strategy for combatting antibiotic-resistant/tolerant bacteria. Herein, we report that a 5-min sublethal heat shock enhances the bactericidal actions of aminoglycoside antibiotics by six orders of magnitude against both exponential- and stationary-phase Escherichia coli. This combined treatment also effectively kills various E. coli persisters, E. coli clinical isolates, and numerous gram-negative but not gram-positive bacteria and enables aminoglycosides at 5% of minimum inhibitory concentrations to eradicate multidrug-resistant pathogens Acinetobacter baumannii and Klebsiella pneumoniae. Mechanistically, the potentiation is achieved comprehensively by heat shock-enhanced proton motive force that thus promotes the bacterial uptake of aminoglycosides, as well as by increasing irreversible protein aggregation and reactive oxygen species that further augment the downstream lethality of aminoglycosides. Consistently, protonophores, chemical chaperones, antioxidants, and anaerobic culturing abolish heat shock-enhanced aminoglycoside lethality. We also demonstrate as a proof of concept that infrared irradiation- or photothermal nanosphere-induced thermal treatments potentiate aminoglycoside killing of Pseudomonas aeruginosa in a mouse acute skin wound model. Our study advances the understanding of the mechanism of actions of aminoglycosides and demonstrates a high potential for thermal ablation in curing bacterial infections when combined with aminoglycosides.
Assuntos
Aminoglicosídeos , Antibacterianos , Camundongos , Animais , Antibacterianos/farmacologia , Antibacterianos/química , Aminoglicosídeos/farmacologia , Aminoglicosídeos/química , Espécies Reativas de Oxigênio/farmacologia , Agregados Proteicos , Escherichia coli , Bactérias Gram-Negativas , Bactérias , Resposta ao Choque Térmico , Testes de Sensibilidade MicrobianaRESUMO
Improving the efficacy of existing antibiotics is a promising strategy for combating antibiotic-resistant/tolerant bacterial pathogens that have become a severe threat to human health. We previously reported that aminoglycoside antibiotics could be dramatically potentiated against stationary-phase Escherichia coli cells under hypoionic shock conditions (i.e., treatment with ion-free solutions), but the underlying molecular mechanism remains unknown. Here, we show that mechanosensitive (MS) channels, a ubiquitous protein family sensing mechanical forces of cell membrane, mediate such hypoionic shock-induced aminoglycoside potentiation. Two-minute treatment under conditions of hypoionic shock (e.g., in pure water) greatly enhances the bactericidal effects of aminoglycosides against both spontaneous and triggered E. coli persisters, numerous strains of Gram-negative pathogens in vitro, and Pseudomonas aeruginosa in mice. Such potentiation is achieved by hypoionic shock-enhanced bacterial uptake of aminoglycosides and is linked to hypoionic shock-induced destabilization of the cytoplasmic membrane in E. coli. Genetic and biochemical analyses reveal that MscS-family channels directly and redundantly mediate aminoglycoside uptake upon hypoionic shock and thus potentiation, with MscL channel showing reduced effect. Molecular docking and site-directed mutagenesis analyses reveal a putative streptomycin-binding pocket in MscS, critical for streptomycin uptake and potentiation. These results suggest that hypoionic shock treatment destabilizes the cytoplasmic membrane and thus changes the membrane tension, which immediately activates MS channels that are able to effectively transport aminoglycosides into the cytoplasm for downstream killing. Our findings reveal the biological effects of hypoionic shock on bacteria and can help to develop novel adjuvants for aminoglycoside potentiation to combat bacterial pathogens via activating MS channels.
Assuntos
Aminoglicosídeos , Proteínas de Escherichia coli , Aminoglicosídeos/química , Aminoglicosídeos/farmacologia , Animais , Antibacterianos/farmacologia , Bactérias , Escherichia coli , Proteínas de Escherichia coli/genética , Canais Iônicos , Camundongos , Simulação de Acoplamento MolecularRESUMO
The COVID-19 outbreak in China appears to reach the late stage since late March 2020, and a stepwise restoration of economic operations is implemented. Risk assessment for such economic restoration is of significance. Here, we estimated the probability of COVID-19 resurgence caused by work resuming in typical provinces/cities and found that such probability is very limited (<5% for all the regions except Beijing). Our work may inform provincial governments to make risk level-based, differentiated control measures.
Assuntos
Infecções por Coronavirus/epidemiologia , Infecções por Coronavirus/transmissão , Surtos de Doenças/estatística & dados numéricos , Pneumonia Viral/epidemiologia , Pneumonia Viral/transmissão , Probabilidade , Retorno ao Trabalho/estatística & dados numéricos , Medição de Risco/estatística & dados numéricos , Adulto , Betacoronavirus , COVID-19 , China/epidemiologia , Cidades , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Pandemias , Recidiva , SARS-CoV-2RESUMO
DegP, a periplasmic dual-functional protease and chaperone in Gram-negative bacteria, is critical for bacterial stress resistance, but the precise underlying mechanisms are not fully understood. Here, we show that the protease function of DegP is critical for Escherichia coli cells to maintain membrane integrity, particularly under heat shock conditions (42°C). Site-directed photo-cross-linking, mass spectrometry and immunoblotting analyses reveal that both periplasmic proteins (e.g. OppA and MalE) and ß-barrel outer membrane proteins (OMPs) are DegP-interacting proteins and that OppA is degraded by DegP in vitro and in vivo at 42°C. In addition, OmpA and BamA, chimeric ß-barrel OMPs containing a soluble periplasmic domain, are bound to DegP in both unfolded and folded forms, whereas only the unfolded forms are degradable by DegP. The presence of folded OmpA as a substrate of DegP is attributed to its periplasmic domain, which is resistant to DegP degradation and even generally protects pure ß-barrel OMPs from degradation in an intra-molecular way. Furthermore, a pair of residues (R262 and V328) in the PDZ domain-1 of DegP play important roles for binding unfolded and folded ß-barrel OMPs, with R262 being critical. Our study, together with earlier reports, indicates that DegP plays a critical role in protein quality control in the bacterial periplasm by degrading both periplasmic proteins and ß-barrel OMPs under stress conditions and likely also by participating in the folding of chimeric ß-barrel OMPs. A working model is proposed to illustrate the finely tuned functions of DegP with respect to different substrate proteins.
Assuntos
Escherichia coli/metabolismo , Proteínas de Choque Térmico/metabolismo , Resposta ao Choque Térmico/fisiologia , Proteínas Periplásmicas/metabolismo , Proteólise , Serina Endopeptidases/metabolismo , Proteínas da Membrana Bacteriana Externa/metabolismo , Proteínas de Escherichia coli/metabolismo , Temperatura Alta , Lipoproteínas , Periplasma/metabolismo , Proteínas Periplásmicas de Ligação/metabolismo , Domínios Proteicos , Desdobramento de ProteínaRESUMO
Protein-protein interaction, including protein homo-oligomerization, is commonly believed to occur through a specific interface made of a limited number of amino acid residues. Here our systematic in vivo photo-crosslinking analysis via genetically incorporated unnatural amino acids unexpectedly shows that the dimerization of HdeA, an acid stress chaperone, is mediated by the residues along its whole polypeptide. These include those "forbidden" residues that are far away from the dimerization interface as judged according to the reported 3-D structure. We demonstrate that such dimerization, though intriguing, is neither a result of protein over-expression nor of any structural disturbance caused by the residue replacement. Similar unexpected dimerization also occurs for two other oligomeric proteins, IbpB (a molecular chaperone existing as polydispersed oligomers in vitro) and DegP (a protease existing as hexamers in vitro). In contrast to these three proteins, dimerization of a few other oligomeric proteins (e.g., OmpF, LamB, SurA, FtsZ and FkpA) that we similarly examined in living cells seems to be mediated only by specific residues. Together, our unexpected observations suggest that, for some oligomeric proteins such as HdeA, IbpB and DegP, their subunit interactions in living cells can also be mediated by residues other than those located at the interfaces as revealed by in vitro structure determination. Our observations might be partially explained by the formation of "encounter complex" or by protein conformational dynamics. Our findings provide new insights on understanding protein-protein interactions and encounter complex formation in living cells.
Assuntos
Proteínas de Escherichia coli/química , Domínios e Motivos de Interação entre Proteínas , Benzofenonas/química , Benzofenonas/metabolismo , Reagentes de Ligações Cruzadas , Diazometano/análogos & derivados , Diazometano/química , Diazometano/metabolismo , Escherichia coli/genética , Escherichia coli/metabolismo , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Proteínas de Choque Térmico/química , Proteínas de Choque Térmico/genética , Proteínas de Choque Térmico/metabolismo , Lisina/análogos & derivados , Lisina/química , Lisina/metabolismo , Modelos Moleculares , Simulação de Dinâmica Molecular , Mutação , Proteínas Periplásmicas/química , Proteínas Periplásmicas/genética , Proteínas Periplásmicas/metabolismo , Fenilalanina/análogos & derivados , Fenilalanina/química , Fenilalanina/metabolismo , Multimerização Proteica , Estrutura Quaternária de Proteína , Subunidades Proteicas , Serina Endopeptidases/química , Serina Endopeptidases/genética , Serina Endopeptidases/metabolismoRESUMO
ß-barrel outer membrane proteins (OMPs) are ubiquitously present in Gram-negative bacteria, mitochondria and chloroplasts, and function in a variety of biological processes. The mechanism by which the hydrophobic nascent ß-barrel OMPs are transported through the hydrophilic periplasmic space in bacterial cells remains elusive. Here, mainly via unnatural amino acid-mediated in vivo photo-crosslinking studies, we revealed that the primary periplasmic chaperone SurA interacts with nascent ß-barrel OMPs largely via its N-domain but with ß-barrel assembly machine protein BamA mainly via its satellite P2 domain, and that the nascent ß-barrel OMPs interact with SurA via their N- and C-terminal regions. Additionally, via dual in vivo photo-crosslinking, we demonstrated the formation of a ternary complex involving ß-barrel OMP, SurA, and BamA in cells. More importantly, we found that a supercomplex spanning the inner and outer membranes and involving the BamA, BamB, SurA, PpiD, SecY, SecE, and SecA proteins appears to exist in living cells, as revealed by a combined analyses of sucrose-gradient ultra-centrifugation, Blue native PAGE and mass spectrometry. We propose that this supercomplex integrates the translocation, transportation, and membrane insertion events for ß-barrel OMP biogenesis.
Assuntos
Proteínas da Membrana Bacteriana Externa/metabolismo , Membrana Celular/metabolismo , Proteínas de Escherichia coli/metabolismo , Escherichia coli/metabolismo , Complexos Multiproteicos/metabolismo , Proteínas da Membrana Bacteriana Externa/química , Proteínas da Membrana Bacteriana Externa/genética , Membrana Celular/química , Membrana Celular/genética , Escherichia coli/química , Escherichia coli/genética , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/genética , Complexos Multiproteicos/química , Complexos Multiproteicos/genéticaRESUMO
Reactive oxygen species (ROS) are important factors mediating aging according to the free radical theory of aging. Few studies have systematically measured ROS levels in relationship to aging, partly due to the lack of tools for detection of specific ROS in live animals. By using the H2O2-specific fluorescence probe Peroxy Orange 1, we assayed the H2O2 levels of live Caenorhabditis elegans with 41 aging-related genes being individually knocked down by RNAi. Knockdown of 14 genes extends the lifespan but increases H2O2 level or shortens the lifespan but decreases H2O2 level, contradicting the free radical theory of aging. Strikingly, a significant inverse correlation between lifespan and the normalized standard deviation of H2O2 levels was observed (p < 0.0001). Such inverse correlation was also observed in worms cultured under heat shock conditions. An oxidative fluctuation hypothesis of aging is thus proposed and suggests that the ability of animals to homeostatically maintain the ROS levels within a narrow range is more important for lifespan extension than just minimizing the ROS levels though the latter still being crucial.
Assuntos
Envelhecimento , Caenorhabditis elegans/fisiologia , Peróxido de Hidrogênio/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Animais , Caenorhabditis elegans/genética , Longevidade , Estresse Oxidativo , Interferência de RNARESUMO
The outer membrane proteins (OMPs) of Gram-negative bacterial cells, as well as the mitochondrion and chloroplast organelles, possess unique and highly stable ß-barrel structures. Biogenesis of OMPs in Escherichia coli involves such periplasmic chaperones as SurA and Skp. In this study, we found that the ΔsurA Δskp double-deletion strain of E. coli, although lethal and defective in the biogenesis of OMPs at the normal growth temperature, is viable and effective at the heat shock temperature. We identified FkpA as the multicopy suppressor for the lethal phenotype of the ΔsurA Δskp strain. We also demonstrated that the deletion of fkpA from the ΔsurA cells resulted in only a mild decrease in the levels of folded OMPs at the normal temperature but a severe decrease as well as lethality at the heat shock temperature, whereas the deletion of fkpA from the Δskp cells had no detectable effect on OMP biogenesis at either temperature. These results strongly suggest a functional redundancy between FkpA and SurA for OMP biogenesis under heat shock stress conditions. Mechanistically, we found that FkpA becomes a more efficient chaperone for OMPs under the heat shock condition, with increases in both binding rate and affinity. In light of these observations and earlier reports, we propose a temperature-responsive OMP biogenesis mechanism in which the degrees of functional importance of the three chaperones are such that SurA > Skp > FkpA at the normal temperature but FkpA ≥ SurA > Skp at the heat shock temperature.
Assuntos
Proteínas da Membrana Bacteriana Externa/metabolismo , Proteínas de Escherichia coli/metabolismo , Escherichia coli/metabolismo , Temperatura Alta , Proteínas de Membrana/metabolismo , Peptidilprolil Isomerase/metabolismo , Proteínas da Membrana Bacteriana Externa/genética , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Deleção de Genes , Regulação Bacteriana da Expressão Gênica/fisiologia , Genótipo , Cinética , Proteínas de Membrana/genética , Chaperonas Moleculares/genética , Chaperonas Moleculares/metabolismo , Peptidilprolil Isomerase/genéticaRESUMO
It is essential for organisms to adapt to fluctuating growth temperatures. Escherichia coli, a model bacterium commonly used in research and industry, has been reported to grow at a temperature lower than 46.5°C. Here we report that the heterologous expression of the 17-kDa small heat shock protein from the nematode Caenorhabditis elegans, CeHSP17, enables E. coli cells to grow at 50°C, which is their highest growth temperature ever reported. Strikingly, CeHSP17 also rescues the thermal lethality of an E. coli mutant deficient in degP, which encodes a protein quality control factor localized in the periplasmic space. Mechanistically, we show that CeHSP17 is partially localized in the periplasmic space and associated with the inner membrane of E. coli, and it helps to maintain the cell envelope integrity of the E. coli cells at the lethal temperatures. Together, our data indicate that maintaining the cell envelope integrity is crucial for the E. coli cells to grow at high temperatures and also shed new light on the development of thermophilic bacteria for industrial application.
Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/metabolismo , Escherichia coli/metabolismo , Escherichia coli/efeitos da radiação , Proteínas de Choque Térmico/metabolismo , Animais , Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/genética , Membrana Celular , Escherichia coli/genética , Deleção de Genes , Proteínas de Choque Térmico/genética , Temperatura Alta , Viabilidade Microbiana , Mutação , Proteínas Periplásmicas/genética , Proteínas Periplásmicas/metabolismo , Serina Endopeptidases/genética , Serina Endopeptidases/metabolismo , Fatores de TempoRESUMO
Small heat shock proteins (sHSPs), as ubiquitous molecular chaperones found in all forms of life, are known to be able to protect cells against stresses and suppress the aggregation of a variety of model substrate proteins under in vitro conditions. Nevertheless, it is poorly understood what natural substrate proteins are protected by sHSPs in living cells. Here, by using a genetically incorporated photo-cross-linker (p-benzoyl-l-phenylalanine), we identified a total of 95 and 54 natural substrate proteins of IbpB (an sHSP from Escherichia coli) in living cells with and without heat shock, respectively. Functional profiling of these proteins (110 in total) suggests that IbpB, although binding to a wide range of cellular proteins, has a remarkable substrate preference for translation-related proteins (e.g. ribosomal proteins and amino-acyl tRNA synthetases) and moderate preference for metabolic enzymes. Furthermore, these two classes of proteins were found to be more prone to aggregation and/or inactivation in cells lacking IbpB under stress conditions (e.g. heat shock). Together, our in vivo data offer novel insights into the chaperone function of IbpB, or sHSPs in general, and suggest that the preferential protection on the protein synthesis machine and metabolic enzymes may dominantly contribute to the well known protective effect of sHSPs on cell survival against stresses.
Assuntos
Reagentes de Ligações Cruzadas/metabolismo , Proteínas de Escherichia coli/metabolismo , Escherichia coli/metabolismo , Proteínas de Choque Térmico/metabolismo , Resposta ao Choque Térmico/fisiologia , Biossíntese de Proteínas/fisiologia , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Proteínas de Choque Térmico/genéticaRESUMO
As ubiquitous molecular chaperones, small heat shock proteins (sHSPs) are crucial for protein homeostasis. It is not clear why sHSPs are able to bind a wide spectrum of non-native substrate proteins and how such binding is enhanced by heat shock. Here, by utilizing a genetically incorporated photo-cross-linker (p-benzoyl-l-phenylalanine), we systematically characterized the substrate-binding residues in IbpB (a sHSP from Escherichia coli) in living cells over a wide spectrum of temperatures (from 20 to 50 °C). A total of 20 and 48 residues were identified at normal and heat shock temperatures, respectively. They are not necessarily hydrophobic and can be classified into three types: types I and II were activated at low and normal temperatures, respectively, and type III mediated oligomerization at low temperature but switched to substrate binding at heat shock temperature. In addition, substrate binding of IbpB in living cells began at temperatures as low as 25 °C and was further enhanced upon temperature elevation. Together, these in vivo data provide novel structural insights into the wide substrate spectrum of sHSPs and suggest that sHSP is able to hierarchically activate its multi-type substrate-binding residues and thus act as a robust chaperone in cells under fluctuating growth conditions.
Assuntos
Proteínas de Escherichia coli/metabolismo , Escherichia coli/metabolismo , Proteínas de Choque Térmico/metabolismo , Resposta ao Choque Térmico/fisiologia , Multimerização Proteica/fisiologia , Sítios de Ligação , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Proteínas de Choque Térmico/genética , Temperatura Alta , Mapeamento de Peptídeos/métodosRESUMO
Small heat shock proteins (sHSPs), as a conserved family of ATP-independent molecular chaperones, are known to bind non-native substrate proteins and facilitate the substrate refolding in cooperation with ATP-dependent chaperones (e.g., DnaK and ClpB). However, how different sHSPs function in coordination is poorly understood. Here we report that IbpA and IbpB, the two sHSPs of Escherichia coli, are coordinated by synchronizing their differential in vivo degradation. Whereas the individually expressed IbpA and IbpB are respectively degraded slowly and rapidly in cells cultured under both heat shock and normal conditions, their simultaneous expression leads to a synchronized degradation at a moderate rate. Apparently, such synchronization is linked to their hetero-oligomerization and cooperation in binding substrate proteins. In addition, truncation of the flexible N- and C-terminal tails dramatically suppresses the IbpB degradation, and somehow accelerates the IbpA degradation. In view of these in vivo data, we propose that the synchronized degradation for IbpA and IbpB are crucial for their synergistic promoting effect on DnaK/ClpB-mediated substrate refolding, conceivably via the formation of IbpA-IbpB-substrate complexes. This scenario may be common for different sHSPs that interact with each other in cells.
Assuntos
Proteínas de Escherichia coli/genética , Escherichia coli/genética , Regulação Bacteriana da Expressão Gênica , Proteínas de Choque Térmico HSP70/genética , Proteínas de Choque Térmico/genética , Endopeptidase Clp , Escherichia coli/metabolismo , Proteínas de Escherichia coli/metabolismo , Proteínas de Choque Térmico HSP70/metabolismo , Meia-Vida , Proteínas de Choque Térmico/metabolismo , Resposta ao Choque Térmico/genética , Temperatura Alta , Ligação Proteica , Multimerização Proteica , Estabilidade Proteica , Estrutura Terciária de Proteína , Proteólise , Especificidade por SubstratoRESUMO
Small heat-shock proteins (sHSPs) are ubiquitous ATP-independent molecular chaperones that play crucial roles in protein quality control in cells. They are able to prevent the aggregation and/or inactivation of various non-native substrate proteins and assist the refolding of these substrates independently or under the help of other ATP-dependent chaperones. Substrate recognition and binding by sHSPs are essential for their chaperone functions. This review focuses on what natural substrate proteins an sHSP protects and how it binds the substrates in cells under fluctuating conditions. It appears that sHSPs of prokaryotes, although being able to bind a wide range of cellular proteins, preferentially protect certain classes of functional proteins, such as translation-related proteins and metabolic enzymes, which may well explain why they could increase the resistance of host cells against various stresses. Mechanistically, the sHSPs of prokaryotes appear to possess numerous multi-type substrate-binding residues and are able to hierarchically activate these residues in a temperature-dependent manner, and thus act as temperature-regulated chaperones. The mechanism of hierarchical activation of substrate-binding residues is also discussed regarding its implication for eukaryotic sHSPs.
Assuntos
Proteínas de Choque Térmico/fisiologia , Chaperonas Moleculares/fisiologia , Ligação ProteicaRESUMO
As an emerging two-dimensional (2D) material, MXene has garnered significant interest in advanced energy storage systems, yet the stackable structure, poor mechanical stability, and lack of moldability limit its large-scale applications. To address this challenge, herein, the self-assembly of MXene on carbonization-free wood was obtained to serve as high-performance electrodes for symmetrical all-wood eco-supercapacitors by a steam-driven self-assembly method. This method can be implemented in a low-temperature environment, significantly simplifying traditional high-temperature annealing processes and generating minimal impact on the environment, human health, and resource consumption. The environmentally friendly steam-driven self-assembly strategy can be further extended into various wood-based electrodes, regardless of the types and structures of wood. As a typical platform electrode, the optimized MXene@delignified balsa wood (MDBW) achieves high areal capacitance and specific capacitance values of 2.99 F cm-2 and 580.55 F g-1 at an extensive mass loading of 5.16 mg cm-2, respectively, with almost loss-free capacitance after 10,000 cycles at 50 mA cm-2. In addition, an all-solid-state symmetrical all-wood eco-supercapacitor was further assembled based on MDBW-20 as both positive and negative electrodes to achieve a high energy density of 19.22 µWh cm-2 at a power density of 0.58 mW cm-2. This work provides an effective strategy to optimize wood-based electrodes for the practical application of biomass eco-supercapacitors.
RESUMO
Fluorination has emerged as a promising strategy in medicinal chemistry to improve the pharmacological profiles of drug candidates. Similarly, incorporating fluorinated non-canonical amino acids into macrocyclic peptides expands chemical diversity and enhances their pharmacological properties, from improved metabolic stability to enhanced cell permeability and target interactions. However, only a limited number of fluorinated non-canonical amino acids, which are canonical amino acid analogs, have been incorporated into macrocyclic peptides by ribosomes for de novo construction and target-based screening of fluorinated macrocyclic peptides. In this study, we report the ribosomal translation of a series of distinct fluorinated non-canonical amino acids, including mono-to tri-fluorinated variants, as well as fluorinated l-amino acids, d-amino acids, ß-amino acids, etc. This enabled the de novo discovery of fluorinated macrocyclic peptides with high affinity for EphA2, and particularly the identification of those exhibiting broad-spectrum activity against Gram-negative bacteria by targeting the BAM complex. This study not only expands the scope of ribosomally translatable fluorinated amino acids but also underscores the versatility of fluorinated macrocyclic peptides as potent therapeutic agents.
RESUMO
Acid chaperones are essential factors in preserving the protein homeostasis for enteric pathogens to survive in the extremely acidic mammalian stomach (pH 1-3). The client proteins of these chaperones remain largely unknown, primarily because of the exceeding difficulty of determining protein-protein interactions under low-pH conditions. We developed a genetically encoded, highly efficient protein photocrosslinking probe, which enabled us to profile the in vivo substrates of a major acid-protection chaperone, HdeA, in Escherichia coli periplasm. Among the identified HdeA client proteins, the periplasmic chaperones DegP and SurA were initially found to be protected by HdeA at a low pH, but they subsequently facilitated the HdeA-mediated acid recovery of other client proteins. This unique, ATP-independent chaperone cooperation in the ATP-deprived E. coli periplasm may support the acid resistance of enteric bacteria. The crosslinker would be valuable in unveiling the physiological interaction partners of any given protein and thus their functions under normal and stress conditions.
Assuntos
Reagentes de Ligações Cruzadas/química , Proteínas de Escherichia coli/metabolismo , Chaperonas Moleculares/química , Chaperonas Moleculares/metabolismo , Ácidos/química , Ácidos/farmacologia , Escherichia coli , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/genética , Concentração de Íons de Hidrogênio , Modelos Moleculares , Estrutura MolecularRESUMO
E(2) (17ß-oestradiol), a female sex hormone, has important biological functions in a woman's body. The pancreas, often considered a non-classical E(2)-targeting organ, is known to be functionally regulated by E(2), but little is known about how oestrogen actions are regulated in this organ. In the present study we report that PDIp (pancreas-specific protein disulfide isomerase), a protein-folding catalyst, can act as a major intracellular E(2) storage protein in a rat model to modulate the pancreatic tissue level, metabolism and action of E(2). The purified endogenous PDIp from both rat and human pancreatic tissues can bind E(2) with a K(d) value of approximately 150 nM. The endogenous PDIp-bound E(2) accounts for over 80% of the total protein-bound E(2) present in rat and human pancreatic tissues, and this binding protects E(2) from metabolic disposition and prolongs its duration of action. Importantly, we showed in ovariectomized female rats that the E(2) level in the pancreas reaches its highest level (9-fold increase over its basal level) at 24-48 h after a single injection of E(2), and even at 96 h its level is still approximately 5-fold higher. In contrast, the E(2) level in the uterus quickly returns to its basal level at 48 h after reaching its maximal level (approximately 2-fold increase) at 24 h. Taken together, these results show for the first time that PDIp is a predominant intracellular oestrogen storage protein in the pancreas, which offers novel mechanistic insights into the accumulation and action of oestrogen inside pancreatic cells.
Assuntos
Estrogênios/metabolismo , Pâncreas/metabolismo , Isomerases de Dissulfetos de Proteínas/metabolismo , Animais , Células COS , Linhagem Celular , Chlorocebus aethiops , Estradiol/metabolismo , Feminino , Humanos , Cinética , Ratos , Ratos Sprague-DawleyRESUMO
Improving the efficacy of existing antibiotics is significant for combatting antibiotic resistance that poses a major threat to human health. Carbonyl cyanide m-chlorophenylhydrazine (CCCP), a well-known protonophore for dissipating proton motive force (PMF), has been widely used to block the PMF-dependent uptake of aminoglycoside antibiotics and thus suppress aminoglycoside lethality. Here, we report that CCCP and its functional analog FCCP, but not other types of protonophores, unprecedently potentiate aminoglycosides (e.g., tobramycin and gentamicin) by 3-4 orders of magnitude killing of Escherichia coli, Staphylococcus aureus, Shigella flexneri, and Vibrio alginolyticus cells in stationary phase but not these cells in exponential phase nor other 12 bacterial species we examined. Overall, the effect of CCCP on aminoglycoside lethality undergoes a gradual transition from suppression against E. coli exponential-phase cells to potentiation against late stationary-phase cells, with the cell growth status and culture medium being crucial. Consistently, disturbance of the PMF by changing transmembrane proton gradient (ΔpH) or electric potential (ΔΨ) also potentiates tobramycin. Nevertheless, CCCP neither increases the intracellular concentration of tobramycin nor decreases the MIC of the antibiotic, thus excluding that CCCP acts as an efflux pump inhibitor to potentiate aminoglycosides. Rather, we show that the combined treatment dramatically enhances the cellular level of hydroxyl radical under both aerobic and anaerobic culturing conditions, under which the antioxidant N-acetyl cysteine fully suppresses both hydroxyl radical accumulation and cell death. Together, these findings open a new avenue to develop certain protonophores as aminoglycoside adjuvants against pathogens in stationary phase and also illustrate an essential role of hydroxyl radical in aminoglycoside lethality regardless of aerobic respiration.
Assuntos
Aminoglicosídeos , Escherichia coli , Humanos , Aminoglicosídeos/farmacologia , Aminoglicosídeos/química , Carbonil Cianeto m-Clorofenil Hidrazona/farmacologia , Radical Hidroxila/farmacologia , Antibacterianos/farmacologia , Tobramicina/farmacologiaRESUMO
Protein disulfide isomerase (PDI) and its pancreatic homolog (PDIp) are folding catalysts for the formation, reduction, and/or isomerization of disulfide bonds in substrate proteins. However, the question as to whether PDI and PDIp can directly attack the native disulfide bonds in substrate proteins is still not answered, which is the subject of the present study. We found that RNase can be thermally unfolded at 65°C under non-reductive conditions while its native disulfide bonds remain intact, and the unfolded RNase can refold and reactivate during cooling. Co-incubation of RNase with PDI or PDIp during thermal unfolding can inactivate RNase in a PDI/PDIp concentration-dependent manner. The alkylated PDI and PDIp, which are devoid of enzymatic activities, cannot inactivate RNase, suggesting that the inactivation of RNase results from the disruption of its native disulfide bonds catalyzed by the enzymatic activities of PDI/PDIp. In support of this suggestion, we show that both PDI and PDIp form stable disulfide-linked complexes only with thermally-unfolded RNase, and RNase in the complexes can be released and reactivated dependently of the redox conditions used. The N-terminal active site of PDIp is essential for the inactivation of RNase. These data indicate that PDI and PDIp can perform thiol-disulfide exchange reactions with native disulfide bonds in unfolded RNase via formation of stable disulfide-linked complexes, and from these complexes RNase is further released.
Assuntos
Dissulfetos/metabolismo , Pâncreas/enzimologia , Isomerases de Dissulfetos de Proteínas/metabolismo , Desdobramento de Proteína , Ribonuclease Pancreático/metabolismo , Temperatura , Alquilação , Animais , Domínio Catalítico , Bovinos , Ativação Enzimática , Estabilidade Enzimática , Dissulfeto de Glutationa/metabolismo , Oxirredução , Fatores de TempoRESUMO
Antibiotic resistance of bacterial pathogens has become a severe threat to human health. To counteract antibiotic resistance, it is of significance to discover new antibiotics and also improve the efficacy of existing antibiotics. Here we show that 5-methylindole, a derivative of the interspecies signaling molecule indole, is able to directly kill various Gram-positive pathogens (e.g., Staphylococcus aureus and Enterococcus faecalis) and also Gram-negative ones (e.g., Escherichia coli and Pseudomonas aeruginosa), with 2-methylindole being less potent. Particularly, 5-methylindole can kill methicillin-resistant S. aureus, multidrug-resistant Klebsiella pneumoniae, Mycobacterium tuberculosis, and antibiotic-tolerant S. aureus persisters. Furthermore, 5-methylindole significantly potentiates aminoglycoside antibiotics, but not fluoroquinolones, killing of S. aureus. In addition, 5-iodoindole also potentiates aminoglycosides. Our findings open a new avenue to develop indole derivatives like 5-methylindole as antibacterial agents or adjuvants of aminoglycoside.