scholarly journals Sequence Variation of Rare Outer Membrane Protein β-Barrel Domains in Clinical Strains Provides Insights into the Evolution ofTreponema pallidumsubsp.pallidum, the Syphilis Spirochete

mBio ◽  
2018 ◽  
Vol 9 (3) ◽  
Author(s):  
Sanjiv Kumar ◽  
Melissa J. Caimano ◽  
Arvind Anand ◽  
Abhishek Dey ◽  
Kelly L. Hawley ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Evolutionary Biology ◽  
Vaccine Development ◽  
Outer Membrane Proteins ◽  
Treponema Pallidum ◽  
Content Type ◽  
Clinical Strains ◽  
Extracellular Loops ◽  
Reference Strains ◽  
Reference Genomes

ABSTRACTIn recent years, considerable progress has been made in topologically and functionally characterizing integral outer membrane proteins (OMPs) ofTreponema pallidumsubspeciespallidum, the syphilis spirochete, and identifying its surface-exposed β-barrel domains. Extracellular loops in OMPs of Gram-negative bacteria are known to be highly variable. We examined the sequence diversity of β-barrel-encoding regions oftprC,tprD, andbamAin 31 specimens from Cali, Colombia; San Francisco, California; and the Czech Republic and compared them to allelic variants in the 41 reference genomes in the NCBI database. To establish a phylogenetic framework, we usedT. pallidum0548 (tp0548) genotyping andtp0558sequences to assign strains to the Nichols or SS14 clades. We found that (i) β-barrels in clinical strains could be grouped according to allelic variants inT. pallidumsubsp.pallidumreference genomes; (ii) for all three OMP loci, clinical strains within the Nichols or SS14 clades often harbored β-barrel variants that differed from the Nichols and SS14 reference strains; and (iii) OMP variable regions often reside in predicted extracellular loops containing B-cell epitopes. On the basis of structural models, nonconservative amino acid substitutions in predicted transmembrane β-strands ofT. pallidumrepeat C (TprC) and TprD2 could give rise to functional differences in their porin channels. OMP profiles of some clinical strains were mosaics of different reference strains and did not correlate with results from enhanced molecular typing. Our observations suggest that human host selection pressures driveT. pallidumsubsp.pallidumOMP diversity and that genetic exchange contributes to the evolutionary biology ofT. pallidumsubsp.pallidum. They also set the stage for topology-based analysis of antibody responses to OMPs and help frame strategies for syphilis vaccine development.IMPORTANCEDespite recent progress characterizing outer membrane proteins (OMPs) ofTreponema pallidum, little is known about how their surface-exposed, β-barrel-forming domains vary among strains circulating within high-risk populations. In this study, sequences for the β-barrel-encoding regions of three OMP loci,tprC,tprD, andbamA, inT. pallidumsubsp.pallidumisolates from a large number of patient specimens from geographically disparate sites were examined. Structural models predict that sequence variation within β-barrel domains occurs predominantly within predicted extracellular loops. Amino acid substitutions in predicted transmembrane strands that could potentially affect porin channel function were also noted. Our findings suggest that selection pressures exerted within human populations driveT. pallidumsubsp.pallidumOMP diversity and that recombination at OMP loci contributes to the evolutionary biology of syphilis spirochetes. These results also set the stage for topology-based analysis of antibody responses that promote clearance ofT. pallidumsubsp.pallidumand frame strategies for vaccine development based upon conserved OMP extracellular loops.

scholarly journals Sequence variation of rare outer membrane protein β-barrel domains in clinical strains provides insights into the evolution ofTreponema pallidumsubsp.pallidum, the syphilis spirochete

2018 ◽  
Author(s):  
Sanjiv Kumar ◽  
Melissa J. Caimano ◽  
Arvind Anand ◽  
Abhishek Dey ◽  
Kelly L. Hawley ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Evolutionary Biology ◽  
Sequence Variation ◽  
Vaccine Development ◽  
Outer Membrane Proteins ◽  
Treponema Pallidum ◽  
Clinical Strains ◽  
Extracellular Loops ◽  
Reference Strains ◽  
Reference Genomes

ABSTRACTIn recent years, considerable progress has been made in topologically and functionally characterizing integral outer membrane proteins (OMPs) ofTreponema pallidumsubspeciespallidum(TPA), the syphilis spirochete, and identifying its surface-exposed β-barrel domains. Extracellular loops in OMPs of Gram-negative bacteria are known to be highly variable. We examined the sequence diversity of β-barrel-encoding regions oftprC,tprD, andbamA, in 31 specimens from Cali, Colombia; San Francisco, California; and the Czech Republic and compared them to allelic variants in the 41 reference genomes in the NCBI database. To establish a phylogenetic framework, we usedtp0548genotyping andtp0558sequences to assign strains to the Nichols or SS14 clades. We found that (i) β-barrels in clinical strains could be grouped according to allelic variants inTPAreference genomes; (ii) for all three OMP loci, clinical strains within the Nichols or SS14 clades often harbored β-barrel variants that differed from the Nichols and SS14 reference strains; and (iii) OMP variable regions often reside in predicted extracellular loops containing B-cell epitopes. Based upon structural models, non-conservative amino acid substitutions in predicted transmembrane β-strands of TprC and TprD2 could give rise to functional differences in their porin channels. OMP profiles of some clinical strains were mosaics of different reference strains and did not correlate with results from enhanced molecular typing. Our observations suggest that human host selection pressures driveTPAOMP diversity and that genetic exchange contributes to the evolutionary biology ofTPA. They also set the stage for topology-based analysis of antibody responses against OMPs and help frame strategies for syphilis vaccine development.IMPORTANCEDespite recent progress characterizing outer membrane proteins (OMPs) ofTreponema pallidum(TPA), little is known about how their surface-exposed, β-barrel-forming domains vary among strains circulating within high-risk populations. In this study, sequences for the β-barrel-encoding regions of three OMP loci,tprC,tprD, andbamA,inTPAfrom a large number of patient specimens from geographically disparate sites were examined. Structural models predict that sequence variation within β-barrel domains occurred predominantly within predicted extracellular loops. Amino acid substitutions in predicted transmembrane strands that could potentially affect porin channel function also were noted. Our findings suggest that selection pressures exerted by human populations driveTPAOMP diversity and that recombination at OMP loci contributes to the evolutionary biology of syphilis spirochetes. These results also set the stage for topology-based analysis of antibody responses that promote clearance ofTPAand frame strategies for vaccine development based upon conserved OMP extracellular loops.

scholarly journals Genetic Similarity of Gonococcal Homologs to Meningococcal Outer Membrane Proteins of Serogroup B Vaccine

mBio ◽  
2019 ◽  
Vol 10 (5) ◽  
Author(s):  
Henju Marjuki ◽  
Nadav Topaz ◽  
Sandeep J. Joseph ◽  
Kim M. Gernert ◽  
Ellen N. Kersh ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Vaccine Development ◽  
Membrane Vesicle ◽  
Outer Membrane Proteins ◽  
The United States ◽  
Cross Protection ◽  
Outer Membrane Vesicle ◽  
Content Type ◽  
Sequence Identity

ABSTRACT The human pathogens Neisseria gonorrhoeae and Neisseria meningitidis share high genome identity. Retrospective analysis of surveillance data from New Zealand indicates the potential cross-protective effect of outer membrane vesicle (OMV) meningococcal serogroup B vaccine (MeNZB) against N. gonorrhoeae. A licensed OMV-based MenB vaccine, MenB-4C, consists of a recombinant FHbp, NhbA, NadA, and the MeNZB OMV. Previous work has identified several abundantly expressed outer membrane proteins (OMPs) as major components of the MenB-4C OMV with high sequence similarity between N. gonorrhoeae and N. meningitidis, suggesting a mechanism for cross-protection. To build off these findings, we performed comparative genomic analysis on 970 recent N. gonorrhoeae isolates collected through a U.S surveillance system against N. meningitidis serogroup B (NmB) reference sequences. We identified 1,525 proteins that were common to both Neisseria species, of which 57 proteins were predicted to be OMPs using in silico methods. Among the MenB-4C antigens, NhbA showed moderate sequence identity (73%) to the respective gonococcal homolog, was highly conserved within N. gonorrhoeae, and was predicted to be surface expressed. In contrast, the gonococcal FHbp was predicted not to be surface expressed, while NadA was absent in all N. gonorrhoeae isolates. Our work confirmed recent observations (E. A. Semchenko, A. Tan, R. Borrow, and K. L. Seib, Clin Infect Dis, 2018, https://doi.org/10.1093/cid/ciy1061) and describes homologous OMPs from a large panel of epidemiologically relevant N. gonorrhoeae strains in the United States against NmB reference strains. Based on our results, we report a set of OMPs that may contribute to the previously observed cross-protection and provide potential antigen targets to guide the next steps in gonorrhea vaccine development. IMPORTANCE Gonorrhea, a sexually transmitted disease, causes substantial global morbidity and economic burden. New prevention and control measures for this disease are urgently needed, as strains resistant to almost all classes of antibiotics available for treatment have emerged. Previous reports demonstrate that cross-protection from gonococcal infections may be conferred by meningococcal serogroup B (MenB) outer membrane vesicle (OMV)-based vaccines. Among 1,525 common proteins shared across the genomes of both N. gonorrhoeae and N. meningitidis, 57 proteins were predicted to be surface expressed (outer membrane proteins [OMPs]) and thus preferred targets for vaccine development. The majority of these OMPs showed high sequence identity between the 2 bacterial species. Our results provide valuable insight into the meningococcal antigens present in the current OMV-containing MenB-4C vaccine that may contribute to cross-protection against gonorrhea and may inform next steps in gonorrhea vaccine development.

scholarly journals Simultaneous detection of LipL32 and LipL21 genes of pathogenic leptospira from serum samples of bovines by multiplex PCR

2011 ◽  
Vol 1 (1) ◽  
pp. 15
Author(s):  
Timiri V. Meenambigai ◽  
Gopalakrishnan Ravikumar ◽  
Andy Srithar ◽  
Govindan Balakrishnan ◽  
Chidambaram Saranya ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Multiplex Pcr ◽  
Outer Membrane ◽  
Vaccine Development ◽  
Outer Membrane Proteins ◽  
Simultaneous Detection ◽  
Serum Samples ◽  
Pathogenic Leptospira ◽  
Annealing Conditions ◽  
Reference Strains

<p>Leptospirosis is a worldwide zoonotic disease of cattle associated with pathogenic leptospiral infection. This study focuses in the use of a molecular tool to detect pathogenic leptospiral infection in bovines by targeting the outer membrane proteins LipL32 and LipL21 simultaneously in a multiplex PCR. Sixteen pathogenic reference strains and 10 bovine serum samples were analyzed for simultaneous detection of both genes at appropriate annealing conditions. These findings are suggestive of the fact that multiplex PCR can be used to detect major outer membrane proteins of pathogenic leptospira from serum samples. Further it aided in the differentiation of pathogenic and non-pathogenic species of leptospires too. This study will definitely serve as a valuable tool, as it suggests the importance of <em>LipL32</em> genes as potential candidates for vaccine development to control animal Leptospirosis.</p>

scholarly journals Linkage between Anaplasma marginale Outer Membrane Proteins Enhances Immunogenicity but Is Not Required for Protection from Challenge

2013 ◽  
Vol 20 (5) ◽  
pp. 651-656 ◽  
Author(s):  
Susan M. Noh ◽  
Joshua E. Turse ◽  
Wendy C. Brown ◽  
Junzo Norimine ◽  
Guy H. Palmer
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Protective Immunity ◽  
Bacterial Infections ◽  
Vaccine Development ◽  
Outer Membrane Proteins ◽  
Anaplasma Marginale ◽  
Anamnestic Response ◽  
Covalent Bonds ◽  
Content Type

ABSTRACTThe prevention of bacterial infections via immunization presents particular challenges. While outer membrane extracts are often protective, they are difficult and expensive to isolate and standardize and thus are often impractical for development and implementation in vaccination programs. In contrast, individual proteins, which are easily adapted for use in subunit vaccines, tend to be poorly protective. Consequently, identification of the specific characteristics of outer membrane-based immunogens, in terms of the antigen contents and contexts that are required for protective immunity, represents a major gap in the knowledge needed for bacterial vaccine development. Using as a modelAnaplasma marginale, a persistent tick-borne bacterial pathogen of cattle, we tested two sets of immunogens to determine whether membrane context affected immunogenicity and the capacity to induce protection. The first immunogen was composed of a complex of outer membrane proteins linked by covalent bonds and known to be protective. The second immunogen was derived directly from the first one, but the proteins were individualized rather than linked. The antibody response induced by the linked immunogen was much greater than that induced by the unlinked immunogen. However, both immunogens induced protective immunity and an anamnestic response. These findings suggest that individual proteins or combinations of proteins can be successfully tested for the ability to induce protective immunity with less regard for overall membrane context. Once protective antigens are identified, immunogenicity could be enhanced by cross-linking to allow a reduced immunogen dose or fewer booster vaccinations.

scholarly journals Immunoproteomic Analysis To Identify Shiga Toxin-Producing Escherichia coli Outer Membrane Proteins Expressed during Human Infection

2014 ◽  
Vol 82 (11) ◽  
pp. 4767-4777 ◽  
Author(s):  
David Montero ◽  
Paz Orellana ◽  
Daniela Gutiérrez ◽  
Daniela Araya ◽  
Juan Carlos Salazar ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Membrane Proteins ◽  
Outer Membrane ◽  
Shiga Toxin ◽  
Vaccine Development ◽  
Outer Membrane Proteins ◽  
Antibiotic Use ◽  
Etiologic Agent ◽  
Human Infection ◽  
Content Type

ABSTRACTShiga-toxin producingEscherichia coli(STEC) is the etiologic agent of acute diarrhea, dysentery, and hemolytic-uremic syndrome (HUS). There is no approved vaccine for STEC infection in humans, and antibiotic use is contraindicated, as it promotes Shiga toxin production. In order to identify STEC-associated antigens and immunogenic proteins, outer membrane proteins (OMPs) were extracted from STEC O26:H11, O103, O113:H21, and O157:H7 strains, and commensalE. colistrain HS was used as a control. SDS-PAGE, two-dimensional-PAGE analysis, Western blot assays using sera from pediatric HUS patients and controls, and matrix-assisted laser desorption ionization–tandem time of flight analyses were used to identify 12 immunogenic OMPs, some of which were not reactive with control sera. Importantly, seven of these proteins have not been previously reported to be immunogenic in STEC strains. Among these seven proteins, OmpT and Cah displayed IgG and IgA reactivity with sera from HUS patients. Genes encoding these two proteins were present in a majority of STEC strains. Knowledge of the antigens produced during infection of the host and the immune response to those antigens will be important for future vaccine development.

scholarly journals Transcriptional and immunological analysis of the putative outer membrane protein and vaccine candidate TprL of Treponema pallidum

2021 ◽  
Vol 15 (1) ◽  
pp. e0008812
Author(s):  
Austin M. Haynes ◽  
Mark Fernandez ◽  
Emily Romeis ◽  
Oriol Mitjà ◽  
Kelika A. Konda ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Vaccine Development ◽  
Vaccine Candidate ◽  
Transcriptional Start Site ◽  
Outer Membrane Proteins ◽  
Treponema Pallidum ◽  
Phase Variation ◽  
Laboratory Animals ◽  
Transcriptional Level ◽  
Development Effort

Background An effective syphilis vaccine should elicit antibodies to Treponema pallidum subsp. pallidum (T. p. pallidum) surface antigens to induce pathogen clearance through opsonophagocytosis. Although the combination of bioinformatics, structural, and functional analyses of T. p. pallidum genes to identify putative outer membrane proteins (OMPs) resulted in a list of potential vaccine candidates, still very little is known about whether and how transcription of these genes is regulated during infection. This knowledge gap is a limitation to vaccine design, as immunity generated to an antigen that can be down-regulated or even silenced at the transcriptional level without affecting virulence would not induce clearance of the pathogen, hence allowing disease progression. Principal findings We report here that tp1031, the T. p. pallidum gene encoding the putative OMP and vaccine candidate TprL is differentially expressed in several T. p. pallidum strains, suggesting transcriptional regulation. Experimental identification of the tprL transcriptional start site revealed that a homopolymeric G sequence of varying length resides within the tprL promoter and that its length affects promoter activity compatible with phase variation. Conversely, in the closely related pathogen T. p. subsp. pertenue, the agent of yaws, where a naturally-occurring deletion has eliminated the tprL promoter region, elements necessary for protein synthesis, and part of the gene ORF, tprL transcription level are negligible compared to T. p. pallidum strains. Accordingly, the humoral response to TprL is absent in yaws-infected laboratory animals and patients compared to syphilis-infected subjects. Conclusion The ability of T. p. pallidum to stochastically vary tprL expression should be considered in any vaccine development effort that includes this antigen. The role of phase variation in contributing to T. p. pallidum antigenic diversity should be further studied.

scholarly journals Global Trends in Proteome Remodeling of the Outer Membrane Modulate Antimicrobial Permeability in Klebsiella pneumoniae

mBio ◽  
2020 ◽  
Vol 11 (2) ◽  
Author(s):  
Andrea Rocker ◽  
Jake A. Lacey ◽  
Matthew J. Belousoff ◽  
Jonathan J. Wilksch ◽  
Richard A. Strugnell ◽  
...  
Keyword(s):  
Antimicrobial Resistance ◽  
Klebsiella Pneumoniae ◽  
Outer Membrane ◽  
Outer Membrane Proteins ◽  
Permeability Barrier ◽  
Significant Finding ◽  
Drug Resistant ◽  
Content Type ◽  
Extracellular Loops

ABSTRACT In Gram-negative bacteria, the permeability of the outer membrane governs rates of antibiotic uptake and thus the efficacy of antimicrobial treatment. Hydrophilic drugs like β-lactam antibiotics depend on diffusion through pore-forming outer membrane proteins to reach their intracellular targets. In this study, we investigated the distribution of porin genes in more than 2,700 Klebsiella isolates and found a widespread loss of OmpK35 functionality, particularly in those strains isolated from clinical environments. Using a defined set of outer-membrane-remodeled mutants, the major porin OmpK35 was shown to be largely responsible for β-lactam permeation. Sequence similarity network analysis characterized the porin protein subfamilies and led to discovery of a new porin family member, OmpK38. Structure-based comparisons of OmpK35, OmpK36, OmpK37, OmpK38, and PhoE showed near-identical pore frameworks but defining differences in the sequence characteristics of the extracellular loops. Antibiotic sensitivity profiles of isogenic Klebsiella pneumoniae strains, each expressing a different porin as its dominant pore, revealed striking differences in the antibiotic permeability characteristics of each channel in a physiological context. Since K. pneumoniae is a nosocomial pathogen with high rates of antimicrobial resistance and concurrent mortality, these experiments elucidate the role of porins in conferring specific drug-resistant phenotypes in a global context, informing future research to combat antimicrobial resistance in K. pneumoniae. IMPORTANCE Klebsiella pneumoniae is a pathogen of humans with high rates of mortality and a recognized global rise in incidence of carbapenem-resistant K. pneumoniae (CRKP). The outer membrane of K. pneumoniae forms a permeability barrier that modulates the ability of antibiotics to reach their intracellular target. OmpK35, OmpK36, OmpK37, OmpK38, PhoE, and OmpK26 are porins in the outer membrane of K. pneumoniae, demonstrated here to have a causative relationship to drug resistance phenotypes in a physiological context. The data highlight that currently trialed combination treatments with a carbapenem and β-lactamase inhibitors could be effective on porin-deficient K. pneumoniae. Together with structural data, the results reveal the role of outer membrane proteome remodeling in antimicrobial resistance of K. pneumoniae and point to the role of extracellular loops, not channel parameters, in drug permeation. This significant finding warrants care in the development of phage therapies for K. pneumoniae infections, given the way porin expression will be modulated to confer phage-resistant—and collateral drug-resistant—phenotypes in K. pneumoniae.

scholarly journals Tight Turns of Outer Membrane Proteins: An Analysis of Sequence, Structure, and Hydrogen Bonding

2018 ◽  
Author(s):  
Meghan Whitney Franklin ◽  
Joanna S.G. Slusky
Keyword(s):  
Hydrogen Bonding ◽  
Membrane Proteins ◽  
Outer Membrane ◽  
Soluble Protein ◽  
Structure Prediction ◽  
Outer Membrane Proteins ◽  
Sequence Structure ◽  
Structural Class ◽  
Future Design ◽  
Extracellular Loops

I.AbstractAs a structural class, tight turns can control molecular recognition, enzymatic activity, and nucleation of folding. They have been extensively characterized in soluble proteins but have not been characterized in outer membrane proteins (OMPs), where they also support critical functions. We clustered the 4-6 residue tight turns of 110 OMPs to characterize the phi/psi angles, sequence, and hydrogen bonding of these structures. We find significant differences between reports of soluble protein tight turns and OMP tight turns. Since OMP strands are less twisted than soluble strands they favor different turn structures types. Moreover, the membrane localization of OMPs yields different sequence hallmarks for their tight turns relative to soluble protein turns. We also characterize the differences in phi/psi angles, sequence, and hydrogen bonding between OMP extracellular loops and OMP periplasmic turns. As previously noted, the extracellular loops tend to be much longer than the periplasmic turns. We find that this difference in length is due to the broader distribution of lengths of the extracellular loops not a large difference in the median length. Extracellular loops also tend to have more charged residues as predicted by the charge-out rule. Finally, in all OMP tight turns, hydrogen bonding between the sidechain and backbone two to four residues away plays an important role. These bonds preferentially use an Asp, Asn, Ser or Thr residue in a beta or pro phi/psi conformation. We anticipate that this study will be applicable to future design and structure prediction of OMPs.

scholarly journals A Disulfide Oxidoreductase (CHU_1165) Is Essential for Cellulose Degradation by Affecting Outer Membrane Proteins in Cytophaga hutchinsonii

2020 ◽  
Vol 86 (8) ◽  
Author(s):  
Dong Zhao ◽  
Ying Wang ◽  
Sen Wang ◽  
Weican Zhang ◽  
Qingsheng Qi ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Disulfide Bond ◽  
Cellulose Degradation ◽  
Outer Membrane Proteins ◽  
Hypothetical Protein ◽  
Pleiotropic Effect ◽  
Content Type ◽  
Cytophaga Hutchinsonii ◽  
Disulfide Oxidoreductase

ABSTRACT Cytophaga hutchinsonii cells can bind to the surface of insoluble cellulose and degrade it by utilizing a novel cell contact-dependent mechanism, in which the outer membrane proteins may play important roles. In this study, the deletion of a gene locus, chu_1165, which encodes a hypothetical protein with 32% identity with TlpB, a disulfide oxidoreductase in Flavobacterium psychrophilum, caused a complete cellulolytic defect in C. hutchinsonii. Further study showed that cells of the Δ1165 strain could not bind to cellulose, and the levels of many outer membrane proteins that can bind to cellulose were significantly decreased. The N-terminal region of CHU_1165 is anchored to the cytoplasmic membrane with five predicted transmembrane helices, and the C-terminal region is predicted to stretch to the periplasm and has a similar thioredoxin (Trx) fold containing a Cys-X-X-Cys motif that is conserved in disulfide oxidoreductases. Recombinant CHU_1165His containing the Cys-X-X-Cys motif was able to reduce the disulfide bonds of insulin in vitro. Site-directed mutation showed that the cysteines in the Cys-X-X-Cys motif and at residues 106 and 108 were indispensable for the function of CHU_1165. Western blotting showed that CHU_1165 was in an oxidized state in vivo, suggesting that it may act as an oxidase to catalyze disulfide bond formation. However, many of the decreased outer membrane proteins that were essential for cellulose degradation contained no or one cysteine, and mutation of the cysteine in these proteins did not affect cellulose degradation, indicating that CHU_1165 may have an indirect or pleiotropic effect on the function of these outer membrane proteins. IMPORTANCE Cytophaga hutchinsonii can rapidly digest cellulose in a contact-dependent manner, in which the outer membrane proteins may play important roles. In this study, a hypothetical protein, CHU_1165, characterized as a disulfide oxidoreductase, is essential for cellulose degradation by affecting the cellulose binding ability of many outer membrane proteins in C. hutchinsonii. Disulfide oxidoreductases are involved in disulfide bond formation. However, our studies show that many of the decreased outer membrane proteins that were essential for cellulose degradation contained no or one cysteine, and mutation of cysteine did not affect their function, indicating that CHU_1165 did not facilitate the formation of a disulfide bond in these proteins. It may have an indirect or pleiotropic effect on the function of these outer membrane proteins. Our study provides an orientation for exploring the proteins that assist in the appropriate conformation of many outer membrane proteins essential for cellulose degradation, which is important for exploring the novel mechanism of cellulose degradation in C. hutchinsonii.

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