Archaeosortases and exosortases are widely distributed systems linking membrane transit with posttranslational modification

J Bacteriol. 2012 Jan;194(1):36-48. doi: 10.1128/JB.06026-11. Epub 2011 Oct 28.

Abstract

Multiple new prokaryotic C-terminal protein-sorting signals were found that reprise the tripartite architecture shared by LPXTG and PEP-CTERM: motif, TM helix, basic cluster. Defining hidden Markov models were constructed for all. PGF-CTERM occurs in 29 archaeal species, some of which have more than 50 proteins that share the domain. PGF-CTERM proteins include the major cell surface protein in Halobacterium, a glycoprotein with a partially characterized diphytanylglyceryl phosphate linkage near its C terminus. Comparative genomics identifies a distant exosortase homolog, designated archaeosortase A (ArtA), as the likely protein-processing enzyme for PGF-CTERM. Proteomics suggests that the PGF-CTERM region is removed. Additional systems include VPXXXP-CTERM/archeaosortase B in two of the same archaea and PEF-CTERM/archaeosortase C in four others. Bacterial exosortases often fall into subfamilies that partner with very different cohorts of extracellular polymeric substance biosynthesis proteins; several species have multiple systems. Variant systems include the VPDSG-CTERM/exosortase C system unique to certain members of the phylum Verrucomicrobia, VPLPA-CTERM/exosortase D in several alpha- and deltaproteobacterial species, and a dedicated (single-target) VPEID-CTERM/exosortase E system in alphaproteobacteria. Exosortase-related families XrtF in the class Flavobacteria and XrtG in Gram-positive bacteria mark distinctive conserved gene neighborhoods. A picture emerges of an ancient and now well-differentiated superfamily of deeply membrane-embedded protein-processing enzymes. Their target proteins are destined to transit cellular membranes during their biosynthesis, during which most undergo additional posttranslational modifications such as glycosylation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Aminoacyltransferases / genetics
  • Aminoacyltransferases / metabolism*
  • Archaeal Proteins / genetics
  • Archaeal Proteins / metabolism*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Cell Membrane
  • Cysteine Endopeptidases / genetics
  • Cysteine Endopeptidases / metabolism*
  • Gene Expression Regulation, Archaeal / physiology
  • Gene Expression Regulation, Bacterial / physiology
  • Gene Expression Regulation, Enzymologic / physiology
  • Molecular Sequence Data
  • Protein Processing, Post-Translational / physiology*

Substances

  • Archaeal Proteins
  • Bacterial Proteins
  • Aminoacyltransferases
  • Cysteine Endopeptidases