Changes in the properties and molecular weights of Bacillus subtilis M-type and N-type alpha-amylases resulting from a spontaneous deletion.

The regulatory gene, amyR2, and the structural gene, amyEn+, coding for N-type alpha-amylase from Bacillus subtilis N7 have been cloned in the B. subtilis plasmid pUB110. The complete nucleotide sequence of amyR2 and amyEn+ has been determined. Starting from an ATG initiator codon, there was an open reading frame comprising 477 amino acids (1,431 bp), giving a molecular weight of 52,678. The NH2-terminal portion of amyEn+ encoded a 41-amino acid-long signal sequence. The DNA nucleotide sequence was compared with the sequences of amyEm+ coding for M-type alpha-amylase from B. subtilis NA64 (Yamazaki et al. (1983) J. Bacteriol. 156, 327-337) and another B. subtilis alpha-amylase gene (Yang et al. (1983) Nucl. Acids Res. 11, 237-249). Almost all the sequences were identical in the three genes. However in the sequence of amyEn+ 32 bp of the other two alpha-amylase genes were deleted in the region from nucleotide 1,406 to 1,437. This deletion region was included in the direct repeat structure of the two genes. The reading frame downstream of the deletion region of amyEn+ shifted and a new termination codon (TGA) appeared at 26 bp downstream. Thus, the differences of the M-type and N-type alpha-amylases from amyEm+ and amyEn+ seemed to be caused by the occurrence of translation termination at different sites of the alpha-amylase gene.