Molecular cloning and sequencing of the upstream region of the major Bacillus subtilis autolysin gene: a modifier protein exhibiting sequence homology to the major autolysin and the spoIID product.

The upstream region of the N-acetylmuramoyl-L-alanine amidase gene (cwlB; a major Bacillus subtilis autolysin) was cloned into Escherichia coli by chromosome walking. Sequencing of the region showed the presence of two open reading frames, one (designated as cwbA) which starts at a UUG codon and encodes a polypeptide of 705 amino acids with an M(r) of 76,725, and the other (designated as lppX), upstream of cwbA, comprising 102 amino acids and having a signal sequence characteristic of a lipoprotein. Purification of the CwbA protein and determination of its N-terminal amino acid sequence revealed that it contains a presumed signal peptide which is processed after Ala at position 25 from the N-terminal, and that the M(r) of the mature form is 75,000. The amino acid sequences of the N-terminal and C-terminal regions of CwbA were found to be highly homologous with those of the cell wall binding domain of CwlB and the spoIID gene product, respectively. CwbA stimulated the major autolysin activity approximately threefold in vitro. These data indicate that CwbA is the modifier protein of the major autolysin reported by Herbold, D. R. & Glaser, L. (1975; Journal of Biological Chemistry 250, 1676-1682). In-frame fusion between the lppX and lacZ genes demonstrated that lppX is translated in vivo and expressed during the exponential growth phase.