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1.
Eur Biophys J ; 49(1): 39-57, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31802151

RESUMO

HasR in the outer membrane of Serratia marcescens binds secreted, heme-loaded HasA and translocates the heme to the periplasm to satisfy the cell's demand for iron. The previously published crystal structure of the wild-type complex showed HasA in a very specific binding arrangement with HasR, apt to relax the grasp on the heme and assure its directed transfer to the HasR-binding site. Here, we present a new crystal structure of the heme-loaded HasA arranged with a mutant of HasR, called double mutant (DM) in the following that seemed to mimic a precursor stage of the abovementioned final arrangement before heme transfer. To test this, we performed first molecular dynamics (MD) simulations starting at the crystal structure of the complex of HasA with the DM mutant and then targeted MD simulations of the entire binding process beginning with heme-loaded HasA in solution. When the simulation starts with the former complex, the two proteins in most simulations do not dissociate. When the mutations are reverted to the wild-type sequence, dissociation and development toward the wild-type complex occur in most simulations. This indicates that the mutations create or enhance a local energy minimum. In the targeted MD simulations, the first protein contacts depend upon the chosen starting position of HasA in solution. Subsequently, heme-loaded HasA slides on the external surface of HasR on paths that converge toward the specific arrangement apt for heme transfer. The targeted simulations end when HasR starts to relax the grasp on the heme, the subsequent events being in a time regime inaccessible to the available computing power. Interestingly, none of the ten independent simulation paths visits exactly the arrangement of HasA with HasR seen in the crystal structure of the mutant. Two factors which do not exclude each other could explain these observations: the double mutation creates a non-physiologic potential energy minimum between the two proteins and /or the target potential in the simulation pushes the system along paths deviating from the low-energy paths of the native binding processes. Our results support the former view, but do not exclude the latter possibility.


Assuntos
Proteínas de Bactérias/química , Proteínas de Transporte/química , Proteínas de Membrana/química , Simulação de Dinâmica Molecular , Receptores de Superfície Celular/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Sítios de Ligação , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Heme/química , Heme/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Mutação , Ligação Proteica , Receptores de Superfície Celular/genética , Receptores de Superfície Celular/metabolismo , Serratia marcescens
2.
Biochem J ; 473(14): 2239-48, 2016 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-27208170

RESUMO

Bacteria use diverse signalling pathways to adapt gene expression to external stimuli. In Gram-negative bacteria, the binding of scarce nutrients to membrane transporters triggers a signalling process that up-regulates the expression of genes of various functions, from uptake of nutrient to production of virulence factors. Although proteins involved in this process have been identified, signal transduction through this family of transporters is not well understood. In the present study, using an integrative approach (EM, SAXS, X-ray crystallography and NMR), we have studied the structure of the haem transporter HasR captured in two stages of the signalling process, i.e. before and after the arrival of signalling activators (haem and its carrier protein). We show for the first time that the HasR domain responsible for signal transfer: (i) is highly flexible in two stages of signalling; (ii) extends into the periplasm at approximately 70-90 Å (1 Å=0.1 nm) from the HasR ß-barrel; and (iii) exhibits local conformational changes in response to the arrival of signalling activators. These features would favour the signal transfer from HasR to its cytoplasmic membrane partners.


Assuntos
Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Proteínas de Membrana Transportadoras/química , Proteínas de Membrana Transportadoras/metabolismo , Cristalografia por Raios X , Heme/metabolismo , Espectroscopia de Ressonância Magnética , Microscopia Eletrônica , Ligação Proteica , Serratia marcescens/metabolismo , Transdução de Sinais/fisiologia
3.
Nat Commun ; 15(1): 331, 2024 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-38184686

RESUMO

Active nutrient uptake is fundamental for survival and pathogenicity of Gram-negative bacteria, which operate a multi-protein Ton system to transport essential nutrients like metals and vitamins. This system harnesses the proton motive force at the inner membrane to energize the import through the outer membrane, but the mechanism of energy transfer remains enigmatic. Here, we study the periplasmic domain of ExbD, a crucial component of the proton channel of the Ton system. We show that this domain is a dynamic dimer switching between two conformations representing the proton channel's open and closed states. By in vivo phenotypic assays we demonstrate that this conformational switch is essential for the nutrient uptake by bacteria. The open state of ExbD triggers a disorder to order transition of TonB, enabling TonB to supply energy to the nutrient transporter. We also reveal the anchoring role of the peptidoglycan layer in this mechanism. Herein, we propose a mechanistic model for the Ton system, emphasizing ExbD duality and the pivotal catalytic role of peptidoglycan. Sequence analysis suggests that this mechanism is conserved in other systems energizing gliding motility and membrane integrity. Our study fills important gaps in understanding bacterial motor mechanism and proposes novel antibacterial strategies.


Assuntos
Peptidoglicano , Prótons , Parede Celular , Nutrientes , Bactérias
4.
Mol Microbiol ; 85(4): 618-31, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22715905

RESUMO

Haem is the major iron source for bacteria that develop in higher organisms. In these hosts, bacteria have to cope with nutritional immunity imposed by the host, since haem and iron are tightly bound to carrier and storage proteins. Siderophores were the first recognized fighters in the battle for iron between bacteria and host. They are non-proteinaceus organic molecules having an extremely high affinity for Fe(3+) and able to extract it from host proteins. Haemophores, that display functional analogy with siderophores, were more recently discovered. They are a class of secreted proteins with a high affinity for haem; they are able to extract haem from host haemoproteins and deliver it to specific receptors that internalize haem. In the past few years, a wealth of data has accumulated on haem acquisition systems that are dependent on surface exposed/secreted bacterial proteins. They promote haem transfer from its initial source (in most cases, a eukaryotic haem binding protein) to the transporter that carries out the membrane crossing step. Here we review recent discoveries in this field, with particular emphasis on similar and dissimilar mechanisms in haemophores and siderophores, from the initial host source to the binding protein/receptor at the cell surface.


Assuntos
Bactérias/metabolismo , Proteínas de Transporte/metabolismo , Hemeproteínas/metabolismo , Ferro/metabolismo , Sideróforos/metabolismo , Bactérias/patogenicidade , Proteínas de Bactérias/metabolismo , Proteínas Ligantes de Grupo Heme , Fatores de Virulência/metabolismo
5.
bioRxiv ; 2023 Aug 11.
Artigo em Inglês | MEDLINE | ID: mdl-37609138

RESUMO

Active nutrient uptake is fundamental for survival and pathogenicity of Gram-negative bacteria, which operate a multi-protein Ton system to transport essential nutrients like metals and vitamins. This system harnesses the proton motive force at the inner membrane to energize the import through the outer membrane, but the mechanism of energy transfer remains enigmatic. Here, we study the periplasmic domain of ExbD, a crucial component of the proton channel of the Ton system. We show that this domain is a dynamic dimer switching between two conformations representing the proton channel's open and closed states. By in vivo phenotypic assays we demonstrate that this conformational switch is essential for the nutrient uptake by bacteria. The open state of ExbD triggers a disorder to order transition of TonB, enabling TonB to supply energy to the nutrient transporter. We also reveal the anchoring role of the peptidoglycan layer in this mechanism. Herein, we propose a mechanistic model for the Ton system, emphasizing ExbD duality and the pivotal catalytic role of peptidoglycan. Sequence analysis suggests that this mechanism is conserved in other systems energizing gliding motility and membrane integrity. Our study fills important gaps in understanding bacterial motor mechanism and proposes novel antibacterial strategies.

6.
Mol Microbiol ; 80(1): 133-48, 2011 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-21276097

RESUMO

Haemophilus influenzae is an obligate human commensal/pathogen. This haem auxotroph must acquire haem from its host to sustain aerobic growth. Haem-haemopexin complexes are one of the potential sources of haem for this microorganism. Haemopexin is a glycoprotein that binds haem with high affinity (subpicomolar Kd) and involved in haem recycling. HxuA, a cell surface protein, is the key to haem acquisition from haemopexin. In this study, we reconstituted a functional Hxu system from H. influenzae in Escherichia coli K-12 that mediated active haem transport across the outer membrane from haem-haemopexin, in the presence of the inner membrane energy-transducing TonB-ExbB-ExbD complex from H. influenzae. A secreted variant of HxuA, HxuA(dm), was produced in E. coli. HxuA(dm) functionally complemented an hxuA mutant of H. influenzae for haem-haemopexin acquisition. HxuA(dm) interacted with haemopexin and haem-haemopexin, with which it formed high-affinity, stoichiometric complexes. Following the interaction between haem-haemopexin and HxuA(dm), haem was no longer bound to its initial high-affinity site and became accessible to its cognate haem receptor, HxuC. HxuA(dm) and the HxuA(dm)-haemopexin complex do not appear to bind haem at detectable levels (affinities below 10(6) M(-1)). HxuA thus appears to 'release' haem from haem-haemopexin complexes and to prevent haem sequestering by haemopexin.


Assuntos
Proteínas de Bactérias/metabolismo , Haemophilus influenzae/metabolismo , Heme/metabolismo , Hemopexina/metabolismo , Proteínas de Bactérias/genética , Calorimetria , Eletroforese , Escherichia coli K12 , Immunoblotting
7.
Proc Natl Acad Sci U S A ; 106(28): 11719-24, 2009 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-19564607

RESUMO

Because heme is a major iron-containing molecule in vertebrates, the ability to use heme-bound iron is a determining factor in successful infection by bacterial pathogens. Until today, all known enzymes performing iron extraction from heme did so through the rupture of the tetrapyrrol skeleton. Here, we identified 2 Escherichia coli paralogs, YfeX and EfeB, without any previously known physiological functions. YfeX and EfeB promote iron extraction from heme preserving the tetrapyrrol ring intact. This novel enzymatic reaction corresponds to the deferrochelation of the heme. YfeX and EfeB are the sole proteins able to provide iron from exogenous heme sources to E. coli. YfeX is located in the cytoplasm. EfeB is periplasmic and enables iron extraction from heme in the periplasm and iron uptake in the absence of any heme permease. YfeX and EfeB are widespread and highly conserved in bacteria. We propose that their physiological function is to retrieve iron from heme.


Assuntos
Proteínas de Transporte de Cátions/metabolismo , Proteínas de Escherichia coli/metabolismo , Escherichia coli/metabolismo , Heme/química , Proteínas de Ligação ao Ferro/metabolismo , Ferro/metabolismo , Cromatografia Líquida de Alta Pressão , Ferro/química , Espectrometria de Massas , Ligação Proteica , Protoporfirinas/metabolismo , Tetrapirróis/química
8.
Proc Natl Acad Sci U S A ; 106(4): 1045-50, 2009 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-19144921

RESUMO

Gram-negative bacteria use specific heme uptake systems, relying on outer membrane receptors and excreted heme-binding proteins (hemophores) to scavenge and actively transport heme. To unravel the unknown molecular details involved, we present 3 structures of the Serratia marcescens receptor HasR in complex with its hemophore HasA. The transfer of heme over a distance of 9 A from its high-affinity site in HasA into a site of lower affinity in HasR is coupled with the exergonic complex formation of the 2 proteins. Upon docking to the receptor, 1 of the 2 axial heme coordinations of the hemophore is initially broken, but the position and orientation of the heme is preserved. Subsequently, steric displacement of heme by a receptor residue ruptures the other axial coordination, leading to heme transfer into the receptor.


Assuntos
Proteínas de Bactérias/química , Proteínas de Transporte/química , Membrana Celular/metabolismo , Heme/metabolismo , Hemeproteínas/química , Proteínas de Membrana/química , Receptores de Superfície Celular/química , Serratia marcescens/química , Apoproteínas/química , Apoproteínas/metabolismo , Proteínas de Bactérias/metabolismo , Transporte Biológico , Calorimetria , Proteínas de Transporte/metabolismo , Cristalografia por Raios X , Heme/química , Proteínas Ligantes de Grupo Heme , Hemeproteínas/metabolismo , Ligantes , Proteínas de Membrana/metabolismo , Modelos Moleculares , Estrutura Secundária de Proteína , Receptores de Superfície Celular/metabolismo , Propriedades de Superfície
9.
Commun Biol ; 5(1): 355, 2022 04 13.
Artigo em Inglês | MEDLINE | ID: mdl-35418619

RESUMO

ExbB and ExbD are cytoplasmic membrane proteins that associate with TonB to convey the energy of the proton-motive force to outer membrane receptors in Gram-negative bacteria for iron uptake. The opportunistic pathogen Serratia marcescens (Sm) possesses both TonB and a heme-specific TonB paralog, HasB. ExbBSm has a long periplasmic extension absent in other bacteria such as E. coli (Ec). Long ExbB's are found in several genera of Alphaproteobacteria, most often in correlation with a hasB gene. We investigated specificity determinants of ExbBSm and HasB. We determined the cryo-EM structures of ExbBSm and of the ExbB-ExbDSm complex from S. marcescens. ExbBSm alone is a stable pentamer, and its complex includes two ExbD monomers. We showed that ExbBSm extension interacts with HasB and is involved in heme acquisition and we identified key residues in the membrane domain of ExbBSm and ExbBEc, essential for function and likely involved in the interaction with TonB/HasB. Our results shed light on the class of inner membrane energy machinery formed by ExbB, ExbD and HasB.


Assuntos
Proteínas de Escherichia coli , Serratia marcescens , Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Heme/metabolismo , Ligação Proteica , Serratia marcescens/química , Serratia marcescens/genética , Serratia marcescens/metabolismo
10.
Res Microbiol ; 170(8): 345-357, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31678562

RESUMO

Iron acquisition is an essential aspect of cell physiology for most bacteria. Although much is known about how bacteria initially recognize the various iron sources they can encounter, whether siderophore, heme, host iron/heme binding proteins, much less is known about how the iron containing compounds (Fe2+, Fe3+, Fe3+-siderophore complex or heme) are transported across the cytoplasmic membrane. This last transport step is powered by specific ABC (ATP-Binding-Cassette) transporters, made up of a substrate binding protein (SBP) that delivers its cargo to the TMD (TransMembrane Domain) of the ABC transporter triggering the entry of the substrate inside the cytoplasm upon catalytic activity of the ABC module. This review focuses on structural aspects of the functioning of such ABC transporters with the most part devoted to the substrate binding proteins.


Assuntos
Transportadores de Cassetes de Ligação de ATP/metabolismo , Bactérias/metabolismo , Compostos de Ferro/metabolismo , Transporte Biológico/fisiologia , Membrana Celular/metabolismo , Heme/metabolismo , Proteínas Ligantes de Grupo Heme/metabolismo , Modelos Moleculares , Sideróforos/metabolismo
11.
J Bacteriol ; 190(6): 1866-70, 2008 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-18178744

RESUMO

Serratia marcescens hemTUV genes encoding a potential heme permease were cloned in Escherichia coli recombinant mutant FB827 dppF::Km(pAM 238-hasR). This strain, which expresses HasR, a foreign heme outer membrane receptor, is potentially capable of using heme as an iron source. However, this process is invalidated due to a dppF::Km mutation which inactivates the Dpp heme/peptide permease responsible for heme, dipeptide, and delta-aminolevulinic (ALA) transport through the E. coli inner membrane. We show here that hemTUV genes complement the Dpp permease for heme utilization as an iron source and thus are functional in E. coli. However, hemTUV genes do not complement the Dpp permease for ALA uptake, indicating that the HemTUV permease does not transport ALA. Peptides do not inhibit heme uptake in vivo, indicating that, unlike Dpp permease, HemTUV permease does not transport peptides. HemT, the periplasmic binding protein, binds heme. Heme binding is saturable and not inhibited by peptides that inhibit heme uptake by the Dpp system. Thus, the S. marcescens HemTUV permease and, most likely, HemTUV orthologs present in many gram-negative pathogens form a class of heme-specific permeases different from the Dpp peptide/heme permease characterized in E. coli.


Assuntos
Proteínas de Bactérias/metabolismo , Escherichia coli/enzimologia , Heme/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Serratia marcescens/enzimologia , Ácido Aminolevulínico/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Transporte Biológico , Dipeptídeos/metabolismo , Eletroforese em Gel de Poliacrilamida , Escherichia coli/genética , Escherichia coli/metabolismo , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Teste de Complementação Genética , Ferro/metabolismo , Luminescência , Proteínas de Membrana Transportadoras/genética , Ligação Proteica , Serratia marcescens/genética , Serratia marcescens/metabolismo , Especificidade por Substrato
13.
Artigo em Inglês | MEDLINE | ID: mdl-16511263

RESUMO

Serratia marcescens is able to acquire iron using its haem-acquisition system (;has'), which contains an outer membrane receptor HasR and a soluble haemophore HasA. After secretion, HasA binds free haem in the extracellular medium or extracts it from haemoproteins and delivers it to the receptor. Here, the crystallization of a HasA-HasR complex is reported. HasA and HasR have been overexpressed in Escherichia coli and the complex formed and crystallized. Small platelets and bunches of needles of dimensions 0.01 x 0.1 x 1 mm were obtained. A native data set has been collected to 6.8 A.


Assuntos
Proteínas de Bactérias/isolamento & purificação , Proteínas de Transporte/isolamento & purificação , Heme/química , Proteínas de Membrana/isolamento & purificação , Serratia/química , Sequência de Aminoácidos , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Proteínas de Transporte/química , Proteínas de Transporte/metabolismo , Cristalização , Cristalografia por Raios X , Heme/metabolismo , Substâncias Macromoleculares/química , Substâncias Macromoleculares/isolamento & purificação , Substâncias Macromoleculares/metabolismo , Proteínas de Membrana/química , Proteínas de Membrana/metabolismo , Dados de Sequência Molecular , Serratia/metabolismo
14.
Nat Commun ; 7: 11590, 2016 05 18.
Artigo em Inglês | MEDLINE | ID: mdl-27188378

RESUMO

Haemophilus influenzae is an obligate human commensal/pathogen that requires haem for survival and can acquire it from several host haemoproteins, including haemopexin. The haem transport system from haem-haemopexin consists of HxuC, a haem receptor, and the two-partner-secretion system HxuB/HxuA. HxuA, which is exposed at the cell surface, is strictly required for haem acquisition from haemopexin. HxuA forms complexes with haem-haemopexin, leading to haem release and its capture by HxuC. The key question is how HxuA liberates haem from haemopexin. Here, we solve crystal structures of HxuA alone, and HxuA in complex with the N-terminal domain of haemopexin. A rational basis for the release of haem from haem-haemopexin is derived from both in vivo and in vitro studies. HxuA acts as a wedge that destabilizes the two-domains structure of haemopexin with a mobile loop on HxuA that favours haem ejection by redirecting key residues in the haem-binding pocket of haemopexin.


Assuntos
Proteínas de Bactérias/metabolismo , Haemophilus influenzae/metabolismo , Heme/metabolismo , Receptores de Peptídeos/metabolismo , Animais , Proteínas de Bactérias/química , Escherichia coli , Microscopia Eletrônica de Transmissão , Estrutura Molecular , Coelhos , Difração de Raios X
15.
PLoS One ; 9(4): e89502, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24727671

RESUMO

Bacteria use diverse signaling pathways to control gene expression in response to external stimuli. In Gram-negative bacteria, the binding of a nutrient is sensed by an outer membrane transporter. This signal is then transmitted to an antisigma factor and subsequently to the cytoplasm where an ECF sigma factor induces expression of genes related to the acquisition of this nutrient. The molecular interactions involved in this transmembrane signaling are poorly understood and structural data on this family of antisigma factor are rare. Here, we present the first structural study of the periplasmic domain of an antisigma factor and its interaction with the transporter. The study concerns the signaling in the heme acquisition system (Has) of Serratia marcescens. Our data support unprecedented partially disordered periplasmic domain of an anti-sigma factor HasS in contact with a membrane-mimicking environment. We solved the 3D structure of the signaling domain of HasR transporter and identified the residues at the HasS-HasR interface. Their conservation in several bacteria suggests wider significance of the proposed model for the understanding of bacterial transmembrane signaling.


Assuntos
Proteínas de Bactérias/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Serratia marcescens/metabolismo , Transdução de Sinais/fisiologia , Periplasma/metabolismo , Ligação Proteica
16.
PLoS One ; 8(3): e58964, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23527057

RESUMO

TonB is a key protein in active transport of essential nutrients like vitamin B12 and metal sources through the outer membrane transporters of Gram-negative bacteria. This inner membrane protein spans the periplasm, contacts the outer membrane receptor by its periplasmic domain and transduces energy from the cytoplasmic membrane pmf to the receptor allowing nutrient internalization. Whereas generally a single TonB protein allows the acquisition of several nutrients through their cognate receptor, in some species one particular TonB is dedicated to a specific system. Despite a considerable amount of data available, the molecular mechanism of TonB-dependent active transport is still poorly understood. In this work, we present a structural study of a TonB-like protein, HasB dedicated to the HasR receptor. HasR acquires heme either free or via an extracellular heme transporter, the hemophore HasA. Heme is used as an iron source by bacteria. We have solved the structure of the HasB periplasmic domain of Serratia marcescens and describe its interaction with a critical region of HasR. Some important differences are observed between HasB and TonB structures. The HasB fold reveals a new structural class of TonB-like proteins. Furthermore, we have identified the structural features that explain the functional specificity of HasB. These results give a new insight into the molecular mechanism of nutrient active transport through the bacterial outer membrane and present the first detailed structural study of a specific TonB-like protein and its interaction with the receptor.


Assuntos
Proteínas de Bactérias/química , Proteínas de Membrana/química , Dobramento de Proteína , Sequência de Aminoácidos , Aminoácidos , Proteínas de Bactérias/metabolismo , Sítios de Ligação , Proteínas de Membrana/metabolismo , Modelos Moleculares , Dados de Sequência Molecular , Peptídeos/química , Peptídeos/metabolismo , Ligação Proteica , Conformação Proteica , Estrutura Secundária de Proteína , Alinhamento de Sequência
18.
J Mol Biol ; 378(4): 840-51, 2008 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-18402979

RESUMO

TonB is a cytoplasmic membrane protein required for active transport of various essential substrates such as heme and iron siderophores through the outer membrane receptors of Gram-negative bacteria. This protein spans the periplasm, contacts outer membrane transporters by its C-terminal domain, and transduces energy from the protonmotive force to the transporters. The TonB box, a relatively conserved sequence localized on the periplasmic side of the transporters, has been shown to directly contact TonB. While Serratia marcescens TonB functions with various transporters, HasB, a TonB-like protein, is dedicated to the HasR transporter. HasR acquires heme either freely or via an extracellular heme carrier, the hemophore HasA, that binds to HasR and delivers heme to the transporter. Here, we study the interaction of HasR with a HasB C-terminal domain and compare it with that obtained with a TonB C-terminal fragment. Analysis of the thermodynamic parameters reveals that the interaction mode of HasR with HasB differs from that with TonB, the difference explaining the functional specificity of HasB for HasR. We also demonstrate that the presence of the substrate on the extracellular face of the transporter modifies, via enthalpy-entropy compensation, the interaction with HasB on the periplasmic face. The transmitted signal depends on the nature of the substrate. While the presence of heme on the transporter modifies only slightly the nature of interactions involved between HasR and HasB, hemophore binding on the transporter dramatically changes the interactions and seems to locally stabilize some structural motifs. In both cases, the HasR TonB box is the target for those modifications.


Assuntos
Proteínas da Membrana Bacteriana Externa/química , Proteínas da Membrana Bacteriana Externa/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Proteínas de Membrana/química , Proteínas de Membrana/metabolismo , Fator sigma/química , Fator sigma/metabolismo , Sequência de Aminoácidos , Proteínas da Membrana Bacteriana Externa/genética , Proteínas de Bactérias/genética , Calorimetria , Sequência Conservada , Escherichia coli/química , Escherichia coli/metabolismo , Heme/metabolismo , Proteínas de Membrana/genética , Dados de Sequência Molecular , Ligação Proteica , Alinhamento de Sequência , Serratia marcescens/química , Serratia marcescens/genética , Serratia marcescens/metabolismo , Fator sigma/genética , Transdução de Sinais , Termodinâmica
19.
J Bacteriol ; 189(14): 5379-82, 2007 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-17483227

RESUMO

On the basis of the three-dimensional model of the heme/hemophore TonB-dependent outer membrane receptor HasR, mutants with six-residue deletions in the 11 putative extracellular loops were generated. Although all mutants continued to be active TonB-dependent heme transporters, mutations in three loops abolished hemophore HasA binding both in vivo and in vitro.


Assuntos
Proteínas de Bactérias/metabolismo , Proteínas de Transporte/metabolismo , Heme/metabolismo , Proteínas de Membrana/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Transporte/química , Proteínas de Transporte/genética , Proteínas de Membrana/química , Proteínas de Membrana/genética , Modelos Moleculares , Mutagênese , Mutação , Ligação Proteica , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína
20.
Biomol NMR Assign ; 1(2): 197-9, 2007 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19636864

RESUMO

The backbone and side chain resonance assignments of the periplasmic domain of HasB, the energy transducer for heme active transport through the specific receptor HasR of Serratia marcescens, have been determined as a first step towards its structural study. The BMRB accession code is 15440.


Assuntos
Proteínas de Bactérias/química , Espectroscopia de Ressonância Magnética/métodos , Proteínas de Membrana/química , Serratia marcescens/metabolismo , Sequência de Aminoácidos , Isótopos de Carbono/química , Peso Molecular , Isótopos de Nitrogênio/química , Estrutura Terciária de Proteína , Prótons
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