MOLECULAR-CLONING AND CHARACTERIZATION OF AN ALKALOPHILIC BACILLUS SP C125 GENE HOMOLOGOUS TO BACILLUS-SUBTILIS SECY

A 1.8 kb HindIII DNA fragment containing the sec Y gene of alkalophilic Bacillus sp. C125 has been cloned into plasmid pUC119 using the B. subtilis sec Y gene as a probe. The complete nucleotide sequence of the cloned DNA indicated that it contained one complete ORF and parts of two other ORFs. The similarity of these ORFs to the sequences of the B. subtilis proteins indicated that they were the genes for ribosomal protein L15-Sec Y-adenylate kinase, in that order. The gene product of the alkalophilic Bacillus sp. C125 sec Y homologue was composed of 431 amino acids and its M(r) value has been calculated to be 47 100. The distribution of hydrophobic amino acids in the gene product suggested that the protein was a membrane integrated protein with ten transmembrane segments. The total amino acid sequence of alkalophilic Bacillus sp. C125 sec Y homologue showed 69.7 % homology with that of B. subtilis sec Y. Regions of remarkably high homology (78 % identity) were present in transmembrane regions, and cytoplasmic domains (73 % identity) with less homologous regions present in extracellular domains (43 % identity).