InterPro: IPR020008 Gammaproteobacterial enzyme, C-terminal transmembrane domain

This entry represents a homology domain that is largely restricted to a subset of the gamma proteobacteria that excludes the enterobacteria. This domain is found at the extreme carboxyl-terminus of a diverse set of proteins, most of which are enzymes with conventional signal sequences and with hydrolytic activities: nucleases, proteases, agarases, etc [1]. Species that have this domain at all typically have from 2-15 proteins tagged with this domain at the C terminus. The agarase AgaA from Vibro sp. (strain JT0107) is secreted into the medium, while the same protein heterologously expressed in Escherichia coli is retained in the cell fraction. This suggests cleavage and release in species with this domain. Both this suggestion, and the chemical structure of the domain (motif, hydrophobic predicted transmembrane helix, cluster of basic residues) closely parallels that of the LPXTG/sortase system and the PEP-CTERM/exosortase(EpsH) system.