IDENTIFICATION OF A GENE FRAGMENT WHICH CODES FOR THE 364 AMINO-TERMINAL AMINO-ACID-RESIDUES OF A SECA HOMOLOG FROM BACILLUS-SUBTILIS - FURTHER EVIDENCE FOR THE CONSERVATION OF THE PROTEIN EXPORT APPARATUS IN GRAM-POSITIVE AND GRAM-NEGATIVE BACTERIA

A DNA fragment that codes for the 364 amino-terminal amino acid residues of a putative Bacillus subtilis SecA homologue has been cloned using the Escherichia coli secA gene as a probe. The deduced amino acid sequence showed 58% identity to the amino-terminus of the E. coli SecA protein. A DNA fragment which codes for 275 amino-terminal amino acid residues of the B. subtilis SecA homologue was expressed in E. coli and the corresponding gene product was shown to be recognized by anti-E. coli SecA antibodies. This polypeptide, although only about 30% the size of the E. coli SecA protein, also restored growth of E. coli MM52 (secA(ts)) at the non-permissive temperature and the translocation defect of proOmpA in this mutant was relieved to a substantial extent.