The Netherlands. Summary

SecA is the precursor protein binding subunit of the bacterial precursor protein translocase, which con-sists of the SecY/E protein as integral membrane domain. SecA is an ATPase, and couples the hydroly-sis of ATP to the release of bound precursor proteins to allow their proton-motive-force-driven transloca-tion across the cytoplasmic membrane. A putative ATP-binding motif can be predicted from the amino acid sequence of SecA with homology to the consen-sus Walker A-type motif. The role of this domain is not known. A lysine residue at position 106 at the end of the glycine-rich loop in the A motif of the Bacillus subtilis SecA was replaced by an asparagine through site-directed mutagenesis (K106N SecA). A similar replacement was introduced at an adjacent lysin