Identification of a region of interaction between Escherichia coli SecA and SecY proteins.

SecA ATPase promotes Escherichia coli protein translocation by its association with the preprotein or preprotein-SecB complex, anionic phospholipids, and the other core component of translocase, integral membrane protein SecYEG. Using ligand affinity blotting we demonstrate a direct interaction of SecA with SecY protein. Proteolysis and gene truncation or fusion studies were used to further define this interaction. Our results demonstrate that the carboxyl-terminal third of SecA protein binds to the amino-terminal 107 amino acid residues of SecY protein. The direct demonstration of these interactions culminate studies that have inferred an interaction between SecA and SecYEG, and they are consistent with studies suggesting that this region of SecA interacts with the inner membrane.