The N-acetylmuramoyl-L-alanine amidase encoded by the Bacillus subtilis 168 prophage SPβ

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Abstract
Heat shock ofBacillus subtilisCU1147, a strain lysogenic for SPβc2, a prophage with a thermosensitive repressor, results in phage induction and subsequent cell lysis. Cloning inEscherichia coliand sequencing of a DNA fragment of prophage SPβ led to the identification ofblyA, the gene encoding a 367 amino acid polypetide with a molecular mass of 39.6 kDa. Purified BlyA obtained from theE. coliclone exhibited anN-acetylmuramoyl-L-alanine amidase activity. Insertional mutagenesis confirmed that the latter enzyme was associated with SPβ-phage-mediated ceil lysis. Analysis of the neighbouring sequence suggested that the two ORFs immediately downstream ofblyAand belonging to the same operon encode polypeptides which may be involved in the release of the endolysin. The presence on the chromosomes of B. subtilis or relatedBacillus spp. of other, similar genes, and their possible relationship, is discussed.