This protein is a putative poly-gamma-glutamate capsule biosynthesis protein found in bacteria. Poly-gamma-glutamate is a natural polymer that may be involved in virulence and may help bacteria survive in high salt concentrations. It is a surface-associated protein.
CapA is a putative poly-gamma-glutamate capsule biosynthesis protein found in bacteria. Poly-gamma-glutamate is a natural polymer that may be involved in virulence and may help bacteria survive in high salt concentrations. It is a surface-associated protein [ (PUBMED:16689787) ].
Family alignment:
There are 12422 PGA_cap domains in 12414 proteins in SMART's nrdb database.
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Evolution (species in which this domain is found)
Taxonomic distribution of proteins containing PGA_cap domain.
This tree includes only several representative species. The complete taxonomic breakdown of all proteins with PGA_cap domain is also avaliable.
Click on the protein counts, or double click on taxonomic names to display all proteins containing PGA_cap domain in the selected taxonomic class.
Poly-gamma-glutamate (PGA), a natural polymer, is synthesized by severalbacteria (all Gram-positive), one archaea and one eukaryote. PGA hasdiverse biochemical properties, enabling it to play different roles,depending on the organism and its environment. Indeed, PGA allows bacteriato survive at high salt concentrations and may also be involved invirulence. The minimal gene sets required for PGA synthesis were recentlydefined. There are currently two nomenclatures depending on the PGA finalstatus: cap, for 'capsule', when PGA is surface associated or pgs, for'polyglutamate synthase', when PGA is released. The minimal gene setscontain four genes termed cap or pgs B, C, A and E. The PGA synthesiscomplex is membrane-anchored and uses glutamate and ATP as substrates.Schematically, the reaction may be divided into two steps, PGA synthesisand PGA transport through the membrane. PGA synthesis depends primarily onCapB-CapC (or PgsB-PgsC), whereas PGA transport requires the presence, orthe addition, of CapA-CapE (or PgsAA-PgsE). The synthesis complex isprobably responsible for the stereochemical specificity of PGAcomposition. Finally, PGA may be anchored to the bacterial surface orreleased. An additional enzyme is involved in this reaction: either CapD,a gamma-glutamyl-transpeptidase that catalyses anchorage of the PGA, orPgsS, a hydrolase that facilitates release. The anchoring of PGA to thebacterial surface is important for virulence. All cap genes are thereforepotential targets for inhibitors specifically blocking PGA synthesis oranchorage.
