Carboxy-terminal region of Escherichia coli SecA ATPase is important to promote its protein translocation activity in vivo.

The role of the carboxy-terminal region of E. coli SecA ATPase was investigated by using genetic methods to construct a truncated SecA protein missing the last 66 amino acid residues and by systematically substituting serine for each of four cysteine residues present in this protein. Truncation of SecA or alteration of any of the carboxy-terminal cysteine residues resulted in poor growth and a protein secretion defect, indicating that this region of SecA is important in its protein translocation activity. Biochemical analysis of the altered proteins revealed a modest increase in translocation ATPase activity, suggesting that the carboxy-terminal region of SecA may facilitate the coupling of its ATPase activity to cycles of protein translocation.