Stewart G S, Ellar D J
Biochem J. 1982 Jan 15;202(1):231-41. doi: 10.1042/bj2020231.
The spore-coat fraction from Bacillus megaterium KM, when prepared by extraction of lysozyme-digested integuments with SDS (sodium dodecyl sulphate) and urea, contains three N-terminal residues and a major component of apparent mol.wt. 17500. Electron microscopy of this fraction shows it to consist of an ordered multilamellar structure similar to that which forms the coat region of intact spores. The 17500-dalton protein, which has been purified to homogeneity, has an N-terminal methionine residue, has high contents of glycine, proline, cysteine and acidic amino acids and readily polymerized even in the presence of thiol-reducing agents. It is first synthesized between late Stage IV and early Stage V, which correlates with the morphological appearance of spore coat. Before Stage VI the 17500-dalton protein is extractable from sporangia by SDS in the absence of thiol-reducing reagents. Between Stage VI and release of mature spores the protein becomes resistant to extraction by SDS unless it is supplemented by a thiol-reducing reagent. In addition to that of the spore-coat protein, the timing of synthesis of all the integument proteins was analysed by SDS/polyacrylamide-gel electrophoresis and non-equilibrium pH-gradient electrophoresis. Several integument proteins are conservatively synthesized from as early as 1h after the end of exponential growth (t1), which may reflect protein incorporation into the spore outer membrane.
巨大芽孢杆菌KM的芽孢衣组分，通过用SDS（十二烷基硫酸钠）和尿素提取经溶菌酶消化的被膜制备而成，含有三个N端残基和一个表观分子量为17500的主要组分。该组分的电子显微镜观察显示，它由一种有序的多层结构组成，类似于完整芽孢的芽孢衣区域所形成的结构。已纯化至同质的17500道尔顿蛋白质，具有一个N端甲硫氨酸残基，甘氨酸、脯氨酸、半胱氨酸和酸性氨基酸含量高，即使在存在硫醇还原剂的情况下也容易聚合。它首先在IV期末期和V期早期之间合成，这与芽孢衣的形态出现相关。在VI期之前，17500道尔顿蛋白质在不存在硫醇还原剂的情况下可被SDS从孢子囊中提取出来。在VI期和成熟芽孢释放之间，该蛋白质变得对SDS提取具有抗性，除非添加硫醇还原剂。除了芽孢衣蛋白外，还通过SDS/聚丙烯酰胺凝胶电泳和非平衡pH梯度电泳分析了所有被膜蛋白的合成时间。几种被膜蛋白早在指数生长结束（t1）后1小时就保守地合成，这可能反映了蛋白质掺入孢子外膜。
