Identification of a TcpC-TcpQ Outer Membrane Complex Involved in the Biogenesis of the Toxin-Coregulated Pilus of
            <i>Vibrio cholerae</i>

Bose, Niranjan; Taylor, Ronald K.

doi:10.1128/jb.187.7.2225-2232.2005

Cited by 38 publications

(57 citation statements)

References 42 publications

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“…Protein abundance patterns have been used successfully to deduce protein interactions within transport systems (4,27,50,51,58). It is possible that the loss of stabilizing physical interactions in tad mutant strains may account for some of the abundance defects we observed.…”

Section: Discussionmentioning

confidence: 78%

Outer Membrane Components of the Tad (Tight Adherence) Secreton ofAggregatibacter actinomycetemcomitans

Clock¹,

Planet

Perez³

et al. 2008

J Bacteriol

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Prokaryotic secretion relies on proteins that are widely conserved, including NTPases and secretins, and on proteins that are system specific. The Tad secretion system in Aggregatibacter actinomycetemcomitans is dedicated to the assembly and export of Flp pili, which are needed for tight adherence. Consistent with predictions that RcpA forms the multimeric outer membrane secretion channel (secretin) of the Flp pilus biogenesis apparatus, we observed the RcpA protein in multimers that were stable in the presence of detergent and found that rcpA and its closely related homologs form a novel and distinct subfamily within a well-supported gene phylogeny of the entire secretin gene superfamily. We also found that rcpA-like genes were always linked to Aggregatibacter rcpB-or Caulobacter cpaD-like genes. Using antisera, we determined the localization and gross abundances of conserved (RcpA and TadC) and unique (RcpB, RcpC, and TadD) Tad proteins. The three Rcp proteins (RcpA, RcpB, and RcpC) and TadD, a putative lipoprotein, localized to the bacterial outer membrane. RcpA, RcpC, and TadD were also found in the inner membrane, while TadC localized exclusively to the inner membrane. The RcpA secretin was necessary for wild-type abundances of RcpB and RcpC, and TadC was required for normal levels of all three Rcp proteins. TadC abundance defects were observed in rcpA and rcpC mutants. TadD production was essential for wild-type RcpA and RcpB abundances, and RcpA did not multimerize or localize to the outer membrane without the expression of TadD. These data indicate that membrane proteins TadC and TadD may influence the assembly, transport, and/or function of individual outer membrane Rcp proteins.Aggregatibacter (formerly Actinobacillus) actinomycetemcomitans is a gram-negative, capnophilic coccobacillus, principally known as the etiologic agent of localized aggressive periodontitis (16,25,39). A. actinomycetemcomitans is occasionally able to colonize sites outside of the oral cavity to produce other infections, and it is one of the so-called HACEK organisms, gram-negative bacteria that cause approximately 3% of infective endocarditis cases (20). Clinical isolates of A. actinomycetemcomitans adhere to surfaces nonspecifically and form remarkably strong biofilms (14,15,29). Insertional mutagenesis studies have shown that genes of the tad (tight adherence) locus are necessary for the nonspecific adherence of the bacterium to surfaces, as well as for the phenotypes of rough colony morphology, autoaggregation, and production of type IVb Flp pili (29,31,42,45). Genetic and biochemical analyses have indicated that 13 tad gene products are involved (3,29,31,42,45,66); only the flp-2 product is not (42).tad loci have been identified in over half of the sequenced bacteria and in all of the archaeal genomes that have been completed (45,52). Phylogenetic evidence strongly indicates that many bacterial species have acquired the tad genes from foreign sources, and because of its apparent propensity for horizontal transfer, the tad lo...

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Section: Discussionmentioning

confidence: 78%

Outer Membrane Components of the Tad (Tight Adherence) Secreton ofAggregatibacter actinomycetemcomitans

Clock¹,

Planet

Perez³

et al. 2008

J Bacteriol

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“…The involvement of lipidation in secretin biogenesis was only tested for XpsD where this post translational fatty acylation turned out to be dispensable for secretin function (24). For BfpB and TcpC two small nonlipidated periplasmic proteins have been shown to be required for their stabilization and multimerization respectively (25,11). N-terminal lipidation plays a key role for HxcQ transport and no additional specific partner is required.…”

Section: Discussionmentioning

confidence: 99%

“…This OM component belongs to a family of proteins generically designated as secretins (6). This family also includes members that are involved in type III protein secretion (T3SS), type IV pilus assembly, type IV bundle-forming pili, toxin co-regulated pili, and assembly and export of filamentous phage (7)(8)(9)(10)(11)(12). Therefore, secretins constitute an important group of transporters specialized in the translocation of bulky macromolecules or macromolecular complexes across the OM.…”

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confidence: 99%

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HxcQ Liposecretin Is Self-piloted to the Outer Membrane by Its N-terminal Lipid Anchor

Viarre

Cascales

Ball

et al. 2009

Journal of Biological Chemistry

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Secretins are an unusual and important class of bacterial outer membrane (OM) proteins. They are involved in the transport of single proteins or macromolecular structures such as pili, needle complexes, and bacteriophages across the OM. Secretins are multimeric ring-shaped structures that form large pores in the OM. The targeting of such macromolecular structures to the OM often requires special assistance, conferred by specific pilotins or pilot proteins. Here, we investigated HxcQ, the OM component of the second Pseudomonas aeruginosa type II secretion system. We found that HxcQ forms high molecular mass structures resistant to heat and SDS, revealing its secretin nature. Interestingly, we showed that HxcQ is a lipoprotein. Construction of a recombinant nonlipidated HxcQ (HxcQnl) revealed that lipidation is essential for HxcQ function. Further phenotypic analysis indicated that HxcQnl accumulates as multimers in the inner membrane of P. aeruginosa, a typical phenotype observed for secretins in the absence of their cognate pilotin. Our observations led us to the conclusion that the lipid anchor of HxcQ plays a pilotin role. The self-piloting of HxcQ to the OM was further confirmed by its correct multimeric OM localization when expressed in the heterologous host Escherichia coli. Altogether, our results reveal an original and unprecedented pathway for secretin transport to the OM.

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“…Overnight cultures were diluted 100-fold and inoculated into fresh LB medium containing ampicillin. Cells in the exponential growth phase (OD 600 ϭ 0.3) were then induced with 0.1% (wt/vol) arabinose for 1 h. Cultures (30 ml) were harvested by centrifugation (10,000 ϫ g), and cellular fractionation was carried out similarly to a procedure previously described (7). Briefly, the cell pellet was resuspended in PBS containing polymyxin B sulfate (10,000 U) and incubated on ice for 10 min.…”

Section: Vol 188 2006mentioning

confidence: 99%

Identification and Characterization of RbmA, a Novel Protein Required for the Development of Rugose Colony Morphology and Biofilm Structure in Vibrio cholerae

Fong¹,

et al. 2006

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Phase variation between smooth and rugose colony variants of Vibrio cholerae is predicted to be important for the pathogen's survival in its natural aquatic ecosystems. The rugose variant forms corrugated colonies, exhibits increased levels of resistance to osmotic, acid, and oxidative stresses, and has an enhanced capacity to form biofilms. Many of these phenotypes are mediated in part by increased production of an exopolysaccharide termed VPS. In this study, we compared total protein profiles of the smooth and rugose variants using two-dimensional gel electrophoresis and identified one protein that is present at a higher level in the rugose variant. A mutation in the gene encoding this protein, which does not have any known homologs in the protein databases, causes cells to form biofilms that are more fragile and sensitive to sodium dodecyl sulfate than wild-type biofilms. The results indicate that the gene, termed rbmA (rugosity and biofilm structure modulator A), is required for rugose colony formation and biofilm structure integrity in V. cholerae. Transcription of rbmA is positively regulated by the response regulator VpsR but not VpsT.The etiologic agent of the diarrheal disease cholera (28), Vibrio cholerae, is a facultative human pathogen. It is naturally found in environmental aquatic habitats both as a free-living organism in the water column and in a biofilm state attached to different surfaces, including mucilaginous surfaces of phytoplankton, chitinous surfaces of zooplankton, and abiotic surfaces (16). V. cholerae causes periodic, seasonal outbreaks of disease in regions where it is an established member of the aquatic ecosystem (10,16,32). The occurrence of these outbreaks is likely to be linked to survival strategies used by V. cholerae in various aquatic habitats. In other words, enhanced survival of the organism in the environment increases the numbers of V. cholerae cells, thereby increasing the likelihood of disease. It has been proposed that the organism uses biofilm formation on surfaces and phase variation as survival strategies (57,58,62).Biofilms are surface-attached microbial communities composed of microorganisms and the extrapolymeric substances they produce (12,40,43). Biofilm formation begins with the transport and attachment of the bacterium to surfaces. After the initial attachment, colonization of a surface is mediated by the movement and growth of attached bacteria. Surface colonization then leads to the formation of microcolonies, which are often surrounded by extrapolymeric substances. Further growth of bacteria and continued production of exopolysaccharides lead to the development of mature biofilm structures characterized by pillars and channels. It has been shown that development of these structures depends on biomass growth rate, twitching motility, signaling molecules, and exopolysaccharide production (12,40,43).The sequence of events leading to the initiation of V. cholerae biofilm on abiotic surfaces under laboratory conditions and the genes required for these steps ha...

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Identification of a TcpC-TcpQ Outer Membrane Complex Involved in the Biogenesis of the Toxin-Coregulated Pilus of Vibrio cholerae

Cited by 38 publications

References 42 publications

Outer Membrane Components of the Tad (Tight Adherence) Secreton ofAggregatibacter actinomycetemcomitans

Outer Membrane Components of the Tad (Tight Adherence) Secreton ofAggregatibacter actinomycetemcomitans

HxcQ Liposecretin Is Self-piloted to the Outer Membrane by Its N-terminal Lipid Anchor

Identification and Characterization of RbmA, a Novel Protein Required for the Development of Rugose Colony Morphology and Biofilm Structure in Vibrio cholerae

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