%0 Journal Article %J J Bacteriol %D 2012 %T Archaeosortases and exosortases are widely distributed systems linking membrane transit with posttranslational modification. %A Haft, Daniel H %A Payne, Samuel H %A Jeremy D Selengut %K Amino Acid Sequence %K Aminoacyltransferases %K Archaeal Proteins %K Bacterial Proteins %K Cell Membrane %K Cysteine Endopeptidases %K Gene Expression Regulation, Archaeal %K Gene Expression Regulation, Bacterial %K Gene Expression Regulation, Enzymologic %K Molecular Sequence Data %K Protein Processing, Post-Translational %X

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.

%B J Bacteriol %V 194 %P 36-48 %8 2012 Jan %G eng %N 1 %R 10.1128/JB.06026-11