Guiard B, Lederer F
Biochimie. 1976;58(3):305-16. doi: 10.1016/s0300-9084(76)80437-3.
We are reporting here an analysis of the chymotryptic peptides obtained from the tryptic heme-binding fragment of flavocytochrome b2 (cytochrome b2 core). These results completely establish the sequence of the 96 residue-long fragment, for which preliminary evidence has been published before [24]. We also report full experimental details concerning the automatic degradation, the specific cleavages at the unique arginine and methionine residues, and the analysis of the tryptic peptides. In addition, it is shown that the main heme-binding fragment resulting from cytochrome b2 proteolysis by yeast proteases has an additional glutamic acid residue at the C-terminal end relative to the main tryptic heme-binding fragment. The slight sequence modifications presented here (amide groups and insertion of a lysine residue after position 71) do not substantially modify the comparison with liver microsomal cytochrome b5. A new sequence alignment is proposed for the two proteins, and a few structural considerations are presented, based on the inspection of calf liver cytochrome b5 three-dimensional model [50,51].
我们在此报告对从黄素细胞色素b2（细胞色素b2核心）的胰蛋白酶血红素结合片段获得的胰凝乳蛋白酶肽段的分析。这些结果完全确定了这个96个残基长的片段的序列，之前已经发表过关于该片段的初步证据[24]。我们还报告了关于自动降解、在独特的精氨酸和甲硫氨酸残基处的特异性切割以及胰蛋白酶肽段分析的完整实验细节。此外，结果表明，酵母蛋白酶对细胞色素b2进行蛋白水解产生的主要血红素结合片段相对于主要的胰蛋白酶血红素结合片段在C末端有一个额外的谷氨酸残基。这里呈现的轻微序列修饰（酰胺基团以及在第71位之后插入一个赖氨酸残基）并没有实质性地改变与肝微粒体细胞色素b5的比较。针对这两种蛋白质提出了一个新的序列比对，并基于对小牛肝脏细胞色素b5三维模型的检查[50,51]给出了一些结构方面的考虑。
