Archaeosortase

An archaeosortase is a protein that occurs in the cell membranes of some archaea.[1] Archaeosortases recognize and remove carboxyl-terminal protein sorting signals about 25 amino acids long from secreted proteins. A genome that encodes one archaeosortase may encode over fifty target proteins. The best characterized archaeosortase target is the Haloferax volcanii S-layer glycoprotein, an extensively modified protein with O-linked glycosylations, N-linked glycosylations, and a large prenyl-derived lipid modification toward the C-terminus.[2] Recent work shows that either of two mutations, knockout of the archaeosortase A (artA) gene or permutation of the motif Pro-Gly-Phe (PGF) to Pro-Phe-Gly, blocks attachment of the lipid moiety as well as blocking removal of the PGF-CTERM protein-sorting domain.[3] Thus archaeosortase appears to be a transpeptidase, like sortase, rather than a simple protease.

Archaeosortases are related to exosortases, their uncharacterized counterparts in Gram-negative bacteria. The names of both families of proteins reflect roles analogous to sortases in Gram-positive bacteria, with which they share no sequence homology. The sequences of archaeosortases and exosortases consists mostly of hydrophobic transmembrane helices, which sortases lack. Archaeosortases fall into a number of distinct subtypes, each responsible for recognizing sorting signals with a different signature motif. Archaeosortase A (ArtA) recognizes the PGF-CTERM signal, ArtB recognizes VPXXXP-CTERM, AtrC recognizes PEF-CTERM, and so on; one archaeal genome may encode two different archaeosortase systems.

References

  1. ↑ Haft, Daniel H.; Samuel H. Payne; Jeremy D. Selengut (January 2012). "Archaeosortases and Exosortases Are Widely Distributed Systems Linking Membrane Transit with Posttranslational Modification". J. Bacteriol. 194 (1): 36–48. doi:10.1128/JB.06026-11.
  2. ↑ "Haloferax volcanii archaeosortase is required for motility, mating, and C-terminal processing of the S-layer glycoprotein". Mol Microbiol. 88 (6): 1164–75. Jun 2013. doi:10.1111/mmi.12248. PMID 23651326.
  3. ↑ Abdul Halim, MF; Karch, KR; Zhou, Y; Haft, DH; Garcia, BA; Pohlschroder, M (2016). "Permuting the PGF Signature Motif Blocks both Archaeosortase-Dependent C-Terminal Cleavage and Prenyl Lipid Attachment for the Haloferax volcanii S-Layer Glycoprotein.". J. Bacteriol. 198: 808–15. doi:10.1128/JB.00849-15. PMID 26712937.
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