Exosortase
| Transmembrane exosortase (Exosortase_EpsH) | |||||||
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| Identifiers | |||||||
| Symbol | Exosortase_EpsH | ||||||
| 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.[1][2] 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.[3] In 2018, a study on Zoogloea resiniphila, a bacterium found in activated sludge wastewater treatment plants, showed that PEP-CTERM proteins (and by implication, exosortase as well) are essential to floc formation in some systems.[4] More recently, Parrett, et al. {{PMID:40358234}} showed that cyanoexosortase B, the lone exosortase in the filamentous Cyanobacterium Nostoc punctiforme, is required both for a colony gliding behavior and for completion of the biosynthesis of the UV-absorbing pigment scytonemin. Both processes depend on PEP-CTERM proteins.
References
[edit]- ↑ Haft DH, Paulsen IT, Ward N, Selengut JD (August 2006). "Exopolysaccharide-associated protein sorting in environmental organisms: the PEP-CTERM/EpsH system. Application of a novel phylogenetic profiling heuristic". BMC Biology. 4 29. doi:10.1186/1741-7007-4-29. PMC 1569441. PMID 16930487.
- ↑ Haft DH, Payne SH, Selengut JD (January 2012). "Archaeosortases and exosortases are widely distributed systems linking membrane transit with posttranslational modification". Journal of Bacteriology. 194 (1): 36–48. doi:10.1128/JB.06026-11. PMC 3256604. PMID 22037399.
- ↑ Abdul Halim MF, Rodriguez R, Stoltzfus JD, Duggin IG, Pohlschroder M (May 2018). "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". Molecular Microbiology. 108 (3): 276–287. doi:10.1111/mmi.13935. PMID 29465796.
- ↑ 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 (May 2018). "Both widespread PEP-CTERM proteins and exopolysaccharides are required for floc formation of Zoogloea resiniphila and other activated sludge bacteria". Environmental Microbiology. 20 (5): 1677–1692. Bibcode:2018EnvMi..20.1677G. doi:10.1111/1462-2920.14080. PMID 29473278. S2CID 4341022. Archived from the original on 2021-01-21. Retrieved 2019-12-14.
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