exosortase

{{Short description|Family of integral membrane proteins}}

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| Symbol = Exosortase_EpsH

| Name = Transmembrane exosortase (Exosortase_EpsH)

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| Pfam= PF09721

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Exosortase refers to a family of integral membrane proteins that occur in Gram-negative bacteria that recognizes and cleaves the carboxyl-terminal sorting signal PEP-CTERM.{{cite journal | vauthors = Haft DH, Paulsen IT, Ward N, Selengut JD | title = Exopolysaccharide-associated protein sorting in environmental organisms: the PEP-CTERM/EpsH system. Application of a novel phylogenetic profiling heuristic | journal = BMC Biology | volume = 4 | pages = 29 | date = August 2006 | pmid = 16930487 | pmc = 1569441 | doi = 10.1186/1741-7007-4-29 | doi-access = free }}{{cite journal | vauthors = Haft DH, Payne SH, Selengut JD | title = Archaeosortases and exosortases are widely distributed systems linking membrane transit with posttranslational modification | journal = Journal of Bacteriology | volume = 194 | issue = 1 | pages = 36–48 | date = January 2012 | pmid = 22037399 | pmc = 3256604 | doi = 10.1128/JB.06026-11 | url = }} The name derives from a predicted role analogous to sortase, despite the lack of any detectable sequence homology, and a strong association of exosortase genes with exopolysaccharide or extracellular polymeric substance biosynthesis loci. Many archaea have an archaeosortase, homologous to exosortases rather than to sortases. Archaeosortase A recognizes the signal PGF-CTERM, found at the C-terminus of some archaeal S-layer proteins. Following processing by archaeosortase A, the PGF-CTERM region is gone, and a prenyl-derived lipid anchor is present at the C-terminus instead.

Exosortase has not itself been characterized biochemically. However, site-directed mutagenesis work on archaeosortase A, an archaeal homolog of exosortases, strongly supports the notion of a Cys active site and convergent evolution with sortase family transpeptidases.{{cite journal | vauthors = Abdul Halim MF, Rodriguez R, Stoltzfus JD, Duggin IG, Pohlschroder M | title = Conserved residues are critical for Haloferax volcanii archaeosortase catalytic activity: Implications for convergent evolution of the catalytic mechanisms of non-homologous sortases from archaea and bacteria | journal = Molecular Microbiology | volume = 108 | issue = 3 | pages = 276–287 | date = May 2018 | pmid = 29465796 | doi = 10.1111/mmi.13935 | doi-access = free }} A recent study on Zoogloea resiniphila, a bacterium found in activated sludge wastewater treatment plants, has shown that PEP-CTERM proteins (and by implication, exosortase as well) are essential to floc formation in some systems.{{cite journal | vauthors = Gao N, Xia M, Dai J, Yu D, An W, Li S, Liu S, He P, Zhang L, Wu Z, Bi X, Chen S, Haft DH, Qiu D | title = Both widespread PEP-CTERM proteins and exopolysaccharides are required for floc formation of Zoogloea resiniphila and other activated sludge bacteria | journal = Environmental Microbiology | volume = 20 | issue = 5 | pages = 1677–1692 | date = May 2018 | pmid = 29473278 | doi = 10.1111/1462-2920.14080 | s2cid = 4341022 | url = http://ir.ihb.ac.cn/handle/342005/29334 | access-date = 2019-12-14 | archive-date = 2021-01-21 | archive-url = https://web.archive.org/web/20210121055907/http://ir.ihb.ac.cn/handle/342005/29334 | url-status = dead }}