Abramov Z T, Ermakova L M, Erokhina L I, Izotova L S, Strongin A Ia
Biokhimiia. 1977 Jan;42(1):51-9.
Using polyacrylamide-gel electrophoresis, isoelectric focusing and gel-filtration it was demonstrated that the auxotrophic mutant strains of Bac. subtilis A-50 and their prototrophic revertant strains produce multiple molecular forms of subtilisin. Three of them are the same as the corresponding molecular forms of subtilisin from the wild strain A-50. In different mutant strains the relative amounts of the main three forms varies considerably resulting in the absence of certain forms in several strains. There is the additional minor form of subtilisin possessing high electrophoretic mobility in four prototrophic revertant strains and one Arg--auxotrophic strain of Bac. subtilis A-50. It would be reasonable to suppose that different molecular forms of subtilisin derive from the product of its single structural gene as a result of post-translational modifications (limited proteolysis). This enzyme and probably most, if not all secretory proteins may be synthesised as larger precursors and then specifically modified in the bacterial cell membranes. Thus, certain mutations, without affecting the structural gene of this secretory protein -- subtilisin -- have pronounced effects on this structural gene expression, varying the degree of its product modification and the amount of resulting secretory molecular forms of subtilisin.
通过聚丙烯酰胺凝胶电泳、等电聚焦和凝胶过滤证明，枯草芽孢杆菌A-50的营养缺陷型突变菌株及其原养型回复突变菌株产生多种分子形式的枯草杆菌蛋白酶。其中三种与野生菌株A-50的枯草杆菌蛋白酶相应分子形式相同。在不同的突变菌株中，主要的三种形式的相对含量差异很大，导致几种菌株中某些形式缺失。在枯草芽孢杆菌A-50的四个原养型回复突变菌株和一个精氨酸营养缺陷型菌株中存在具有高电泳迁移率的额外的次要枯草杆菌蛋白酶形式。可以合理推测，枯草杆菌蛋白酶的不同分子形式是其单一结构基因产物经翻译后修饰（有限蛋白水解）的结果。这种酶以及可能大多数（如果不是全部）分泌蛋白可能以较大的前体形式合成，然后在细菌细胞膜中进行特异性修饰。因此，某些突变在不影响这种分泌蛋白——枯草杆菌蛋白酶的结构基因的情况下，对该结构基因的表达有显著影响，改变其产物修饰程度以及产生的枯草杆菌蛋白酶分泌分子形式的量。
