Stewart G S, Ellar D J
Biochem J. 1983 Feb 15;210(2):411-7. doi: 10.1042/bj2100411.
A protein of apparent mol.wt. 35000 that is extractable from the purified coat fraction of Bacillus megaterium KM spores is synthesized during sporulation as a precursor protein from which a 12-13 amino acid peptide is removed. Cleavage of this small peptide is delayed until 60-90 min after precursor synthesis and is concomitant with the morphological appearance of stage VI. The addition of chloramphenicol, subsequent to precursor synthesis, prevents the appearance of this late processing event. Two-dimensional non-equilibrium pH-gradient gel electrophoresis of the integument extract of forespores isolated at stage V from sporangia pulse-labelled with L-[35S]methionine 1 h before isolation, revealed both unprocessed and processed components. Similar analysis of total protein from the corresponding mother cells revealed only the unprocessed component in relatively small amounts, suggesting that, although the protein may be synthesized in the mother-cell compartment, processing may be restricted to the forespore. Peptide analysis by limited proteolysis was used to examine the relationship between the 35000- and a 17500-mol.wt. coat protein. The possible implications of limited proteolytic processing to maturation of the spore coat are discussed.
从巨大芽孢杆菌KM芽孢的纯化外壳组分中可提取出一种表观分子量为35000的蛋白质，它在芽孢形成过程中以前体蛋白的形式合成，该前体蛋白会去除一个12 - 13个氨基酸的肽段。这个小肽段的切割会延迟到前体蛋白合成后60 - 90分钟，并且与VI期的形态出现同时发生。在前体蛋白合成后添加氯霉素会阻止这种后期加工事件的出现。对在分离前1小时用L - [35S]甲硫氨酸脉冲标记的孢子囊在V期分离得到的前芽孢的被膜提取物进行二维非平衡pH梯度凝胶电泳，显示出未加工和已加工的组分。对相应母细胞总蛋白的类似分析仅显示出少量未加工的组分，这表明，尽管该蛋白可能在母细胞区室中合成，但加工可能仅限于前芽孢。通过有限蛋白酶解进行肽分析，以研究分子量为35000和17500的外壳蛋白之间的关系。讨论了有限蛋白酶解加工对芽孢外壳成熟的可能影响。
