Cloning and sequencing of the beta-lactamase I gene of Bacillus cereus 5/B and its expression in Bacillus subtilis

The beta-lactamases of Bacillus cereus have attracted interest because they are secreted efficiently, because multiple enzymes are frequently present, and because their regulation has unusual features. beta-Lactamase I of strain 5/B is produced constitutively at a high level, and the exoenzyme appears to be several thousand daltons larger than the corresponding product of strain 569/H. We have cloned the gene for 5/B beta-lactamase I in Escherichia coli and B. subtilis and have sequenced the structural portion and the regulatory regions. The 5/B enzyme is produced at a low level in E. coli RR1(pRWY200) and remains cellbound. In B. subtilis it is formed in large amounts, and over 90% of it is released into the medium. There is a large degree of homology between the promoter and leader peptide regions of the 5/B and 569/H genes; both utilize UUG as the translation initiation codon (P. S. F. Mézes, R. W. Blacher, and J. O. Lampen, (J. Biol. Chem. 260:1218-1223, 1985). Although there are significant differences in the peptide segment where processing would be expected to occur, the NH2 terminus of the major 5/B product from B. subtilis BD170(pRWY215) is His-44, which is the same as the NH2 terminus of the major 569/H product from B. subtilis BD170(pRWM5).