Effects of mutations in Bacillus subtilis genome decreasing the protease activity on the formation of subtilisin molecular forms]

Multiple molecular forms of subtilisin--extracellular serine protease produced by the wild strain Bac. subtilis A-50 and its mutant strains with the protease activity decreased two-fold and more were studied. Six molecular forms of subtilisin were found on the whole when 33 mutant strains have been investigated under the experimental conditions. It is essential that both the wild and each of mutant strains under study produced not more than three out of these six forms. Three molecular forms of subtilisin from the mutant strains are similar to those found in the wild strain A-50, and have the molecular weight, of 27 000-30 000. Three other forms of subtilisin were revealed only in the mutant strains, and had the molecular weight of about 20 000. Apparently there is only one structural gene for subtilisin in Bac. subtilis genome. The appearence of multiple molecular forms of subtilisin may be due to the post-translational modifications (limited proteolysis) of the initial type of enzyme, i.e. pre-subtilisin. Probably, that certain mulations not affecting the structural gene can significantly change the expression of such gene by varying of the degree of product modifications.