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Gene Review

cvaB  -  colicin V secretion protein; similar to...

Escherichia coli

 
 
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Disease relevance of cvaB

  • Extracellular secretion of the peptide antibiotic colicin V (ColV) in Escherichia coli is mediated by a dedicated exporter system consisting of host TolC protein and the products of two specific genes, cvaA and cvaB, the latter being a member of the ATP binding cassette (ABC) superfamily [1].
  • The three Erwinia protease export proteins can also export active ColV, and interference is seen when CvaA or CvaB is expressed along with the intact Prt exporter [2].
 

High impact information on cvaB

  • The extracellular secretion of the antibacterial toxin colicin V is mediated via a signal sequence independent process which requires the products of two linked genes: cvaA and cvaB [3].
  • The nucleotide sequence of cvaB reveals that its product is a member of a subfamily of proteins, involved in the export of diverse molecules, found in both eukaryotes and prokaryotes [3].
  • Together with comparisons of the sequences of members of the cysteine protease family, these results indicate that Cys32 and His105 are the critical residues in the CvaB N-terminal domain for the calcium-dependent cysteine protease activity and secretion of colicin V [4].
  • The cytoplasmic membrane protein CvaB, involved in colicin V secretion in Escherichia coli, belongs to the ABC-transporter family in which ATP hydrolysis is typically the driving force for substrate transport [5].
  • These included sitABCD, genes of the aerobactin operon, hlyF, iss, genes of the salmochelin operon, and the 5' end of cvaB of the ColV operon [6].
 

Biological context of cvaB

  • Nucleotide binding was shown to be critical for CvaB CTD dimerization [7].
  • Interactions of dedicated export membrane proteins of the colicin V secretion system: CvaA, a member of the membrane fusion protein family, interacts with CvaB and TolC [8].
  • Moreover, a point mutation (D654H) in CvaB that completely abolishes colicin V secretion severely impairs both GTPase and ATPase activities in the corresponding BCTD, indicating that the two activities are from the same enzyme [9].
 

Anatomical context of cvaB

  • As a member of the membrane fusion protein family, CvaA is supposed to form a bridge that connects the inner and outer membranes via interaction with CvaB and TolC, respectively [8].
 

Associations of cvaB with chemical compounds

  • Cys32 and His105 in the N-terminal domain of CvaB were identified as critical residues for both colicin V secretion and cysteine proteolytic activity [4].
 

Analytical, diagnostic and therapeutic context of cvaB

  • Sequence alignment and homology modeling of the CvaB nucleotide-binding domain predicted that the aromatic stacking region of CvaB (Y501DSQ loop) had a role in the differential binding of nucleotides, and Ser503 and Gln504 provided potential hydrogen bonds to GTP but not to ATP [5].
  • Different forms of the CvaB CTD were found during purification and identified as monomer, dimer, and oligomer forms by gel filtration and protein cross-linking [7].

References

  1. Processing of colicin V-1, a secretable marker protein of a bacterial ATP binding cassette export system, requires membrane integrity, energy, and cytosolic factors. Zhong, X., Kolter, R., Tai, P.C. J. Biol. Chem. (1996) [Pubmed]
  2. Functional complementation between bacterial MDR-like export systems: colicin V, alpha-hemolysin, and Erwinia protease. Fath, M.J., Skvirsky, R.C., Kolter, R. J. Bacteriol. (1991) [Pubmed]
  3. Genetic analysis of an MDR-like export system: the secretion of colicin V. Gilson, L., Mahanty, H.K., Kolter, R. EMBO J. (1990) [Pubmed]
  4. Cys32 and His105 are the critical residues for the calcium-dependent cysteine proteolytic activity of CvaB, an ATP-binding cassette transporter. Wu, K.H., Tai, P.C. J. Biol. Chem. (2004) [Pubmed]
  5. Molecular Basis for Differential Nucleotide Binding of the Nucleotide-Binding Domain of ABC-Transporter CvaB. Guo, X., Chen, X., Weber, I.T., Harrison, R.W., Tai, P.C. Biochemistry (2006) [Pubmed]
  6. Complete DNA sequence of a ColBM plasmid from avian pathogenic Escherichia coli suggests that it evolved from closely related ColV virulence plasmids. Johnson, T.J., Johnson, S.J., Nolan, L.K. J. Bacteriol. (2006) [Pubmed]
  7. Nucleotide-dependent dimerization of the C-terminal domain of the ABC transporter CvaB in colicin V secretion. Guo, X., Harrison, R.W., Tai, P.C. J. Bacteriol. (2006) [Pubmed]
  8. Interactions of dedicated export membrane proteins of the colicin V secretion system: CvaA, a member of the membrane fusion protein family, interacts with CvaB and TolC. Hwang, J., Zhong, X., Tai, P.C. J. Bacteriol. (1997) [Pubmed]
  9. When an ATPase is not an ATPase: at low temperatures the C-terminal domain of the ABC transporter CvaB is a GTPase. Zhong, X., Tai, P.C. J. Bacteriol. (1998) [Pubmed]
 
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