THE STRUCTURE OF SUBTILISIN ALP-I FROM ALKALOPHILIC BACILLUS SP NKS-21

The gene for an alkaline serine protease from alkalophilic Bacillus sp . NKS-21 (subtilisin ALP I) was cloned, and its nucleotide sequence wa s determined. The gene (aprQ) contained an open reading frame of 1125 bp, encoding a primary product of 374 amino acids. The mature protease , composed of 272 amino acids, was preceded by a putative signal seque nce of 37 amino acids and a pro-sequence of 65 amino acids. The mature protease conserved the catalytic triad, Asp, His, and Ser, as subtili sin BPN' or other subtilisins, and the subtilisin ALP I might belong t o the subtilisin super family. The primary structure of subtilisin ALP I was compared and discussed with those of 13 subtilisins, 5 subtilis ins from alkalophilic Bacillus, and 8 from neutrophiles. Low homology was shown between subtilisin ALP I and subtilisins from alkalophiles o r subtilisins from neutrophiles. Forty-five amino acid residues of the mature protein of subtilisin ALP I were entirely independent of other subtilisins. According to the homology of ALP I with other subtilisin s, subtilisin ALP I might be in the middle point between alkaline subt ilisins and neutral ones.