Family

Protein translocase complex, SecE/Sec61-gamma subunit (IPR001901)

Short name: Translocase_SecE/Sec61-g

Family relationships

Description

Secretion across the inner membrane in some Gram-negative bacteria occurs via the preprotein translocase pathway. Proteins are produced in the cytoplasm as precursors, and require a chaperone subunit to direct them to the translocase component [PMID: 2202721]. From there, the mature proteins are either targeted to the outer membrane, or remain as periplasmic proteins. The translocase protein subunits are encoded on the bacterial chromosome.

The translocase itself comprises 7 proteins, including a chaperone protein (SecB), an ATPase (SecA), an integral membrane complex (SecCY, SecE and SecG), and two additional membrane proteins that promote the release of the mature peptide into the periplasm (SecD and SecF) [PMID: 2202721]. The chaperone protein SecB [PMID: 11336818] is a highly acidic homotetrameric protein that exists as a "dimer of dimers" in the bacterial cytoplasm. SecB maintains preproteins in an unfolded state after translation, and targets these to the peripheral membrane protein ATPase SecA for secretion [PMID: 10418149]. SecE, part of the main SecYEG translocase complex, is ~106 residues in length, and spans the inner membrane of the Gram-negative bacterial envelope. Together with SecY and SecG, SecE forms a multimeric channel through which preproteins are translocated, using both proton motive forces and ATP-driven secretion. The latter is mediated by SecA.

In eukaryotes, the evolutionary related protein sec61-gamma plays a role in protein translocation through the endoplasmic reticulum; it is part of a trimeric complex that also consist of sec61-alpha and beta [PMID: 8107851]. Both secE and sec61-gamma are small proteins of about 60 to 90 amino acids that contain a single transmembrane region at their C-terminal extremity (Escherichia coli secE is an exception, in that it possess an extra N-terminal segment of 60 residues that contains two additional transmembrane domains) [PMID: 9393849].

GO terms

Biological Process

GO:0006886 intracellular protein transport
GO:0006605 protein targeting

Molecular Function

No terms assigned in this category.

Cellular Component

GO:0016020 membrane

Contributing signatures

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