Conserved Site

Peptidase S26A, signal peptidase I, conserved site (IPR019758)

Short name: Pept_S26A_signal_pept_1_CS


Signal peptidases (SPases) [PMID: 1455520] (also known as leader peptidases) remove the signal peptides from secretory proteins. In prokaryotes three types of SPases are known: type I (gene lepB) which is responsible for the processing of the majority of exported pre-proteins; type II (gene lsp) which only process lipoproteins, and a third type involved in the processing of pili subunits.

SPase I (EC is an integral membrane protein that is anchored in the cytoplasmic membrane by one (in Bacillus subtilis) or two (in Escherichia coli) N-terminal transmembrane domains with the main part of the protein protuding in the periplasmic space. Two residues have been shown [PMID: 1618816, PMID: 8394311] to be essential for the catalytic activity of SPase I: a serine and an lysine.

SPase I is evolutionary related to the yeast mitochondrial inner membrane protease subunit 1 and 2 (genes IMP1 and IMP2) which catalyse the removal of signal peptides required for the targeting of proteins from the mitochondrial matrix, across the inner membrane, into the inter-membrane space [PMID: 8266095].

In eukaryotes the removal of signal peptides is effected by an oligomeric enzymatic complex composed of at least five subunits: the signal peptidase complex (SPC). The SPC is located in the endoplasmic reticulum membrane. Two components of mammalian SPC, the 18 Kd (SPC18) and the 21 Kd (SPC21) subunits as well as the yeast SEC11 subunit have been shown [PMID: 7845208] to share regions of sequence similarity with prokaryotic SPases I and yeast IMP1/IMP2.

This entry represents a conserved region of unknown biological significance which is located in the C-terminal section of S26 peptidases (SPase I and IMP1/2).

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0008236 serine-type peptidase activity

Cellular Component

GO:0016021 integral component of membrane

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
PROSITE patterns