Family

Preprotein translocase SecG subunit (IPR004692)

Short name: SecG

Family relationships

None.

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]. 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.

SecG has two transmembrane domains, both of which contribute to the recognition of preprotein signal sequences by the translocation complex [PMID: 7650029]. The protein also undergoes membrane topology inversion when coupled to the SecA cycle [PMID: 11445571].

GO terms

Biological Process

GO:0009306 protein secretion

Molecular Function

GO:0015450 P-P-bond-hydrolysis-driven protein transmembrane transporter activity

Cellular Component

GO:0016021 integral component of membrane

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
Pfam
TIGRFAMs
PRINTS