SecA is a cytoplasmic protein of 800 to 960 amino acid residues. The
eubacterial secA protein  plays an important role in protein export. It
interacts with the secY and secE components of the protein translocation
system. It has a central role in coupling the hydrolysis of ATP to the
transfer of proteins across the membrane.
SecA is a superfamily 2 (SF2) helicase (see <PDOC51192>) that adapted to
translocate proteins. It contains the characteristic DEAD/DEXH ATPase core
structure with the seven SF2 motifs [2,3].
Several structural analyses on secA have been reported (see <PDB:1M6N>) [4,5].
They show that secA contains two recA-like domains similar to SF1 and SF2
helicases. In helicases, the two recA-like domains move relative to one
another during the ATPase cycle, generating domain movements that translocate
the helicase along nucleic acids. In secA, it seems that a similar mechanism
is used to generate domain movements that are coupled to polypeptide
translocation. The N-terminal recA-like domain of secA contains an insert of
about 150 residues that forms the preprotein crosslinking domain (PPXD) which
has the ability to bind preproteins in solution and which is important for
preprotein loading onto SecYEG-containing membranes .
Homologs of secA are also encoded in the chloroplast genome of some algae 
as well as in the nuclear genome of plants . It could be involved in the
intraorganellar protein transport into thylakoids.
We have developed a signature pattern for secA proteins based on the best
conserved region. This region is located in the C-terminal recA-like domain.
We also developed a profile that covers the region corresponding to the
two recA-like domains.
PROSITE is copyrighted by the SIB Swiss Institute of Bioinformatics and
distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives
(CC BY-NC-ND 4.0) License, see prosite_license.html.