Haumont P Y, Thomas M A, Labeyrie F, Lederer F
Centre National de la Recherche Scientifique Unité Associée 122, Hôpital Necker, Paris, France.
Eur J Biochem. 1987 Dec 15;169(3):539-46. doi: 10.1111/j.1432-1033.1987.tb13642.x.
Flavocytochrome b2 (L-lactate dehydrogenase) from baker's yeast is composed of two structural and functional domains. Its first 100 residues constitute the heme-binding core, which is homologous to cytochrome b5 [B. Guiard, O. Groudinsky & F. Lederer (1974) Proc. Natl Acad. Sci. USA 71, 2539-2543]. We report here the amino acid sequence of the heme-binding domain isolated by tryptic proteolysis of Hansenula anomala flavocytochrome b2. The sequence was established by automated degradation of the whole fragment and of peptides obtained by CNBr cleavage at the unique tryptophan and by proteolysis with thermolysin and endoproteinase Lys C. As isolated, the domain consists of 84 residues without any sulfur amino acids. It shows 49 identities with the heme-binding domain from Saccharomyces cerevisiae and 28 with beef microsomal cytochrome b5. Using the recently published three-dimensional structure of S. cerevisiae flavocytochrome b2 [Z-x. Xia, N. Shamala, P. H. Bethge, L. W. Lim, H. D. Bellamy, N. H. Xuong, F. Lederer and F. S. Mathews (1987) Proc. Natl Acad. Sci. USA 84, 2629-2633], it can be seen that there are only positively charged side chains close to the accessible heme edge, the only negative charges in that area being those of the heme propionates. The implications of this result are discussed in the light of Salemme's model for the cytochrome b5/cytochrome c complex [F. R. Salemme (1976) J. Mol. Biol. 102, 563-568].
来自面包酵母的黄素细胞色素b2（L-乳酸脱氢酶）由两个结构和功能域组成。其前100个残基构成血红素结合核心，该核心与细胞色素b5同源[B. Guiard，O. Groudinsky和F. Lederer（1974年）美国国家科学院院刊71，2539 - 2543]。我们在此报告通过异常汉逊酵母黄素细胞色素b2的胰蛋白酶解所分离的血红素结合域的氨基酸序列。该序列通过对整个片段以及通过在唯一色氨酸处进行CNBr裂解和用嗜热菌蛋白酶及内肽酶Lys C进行蛋白水解所获得的肽段进行自动降解而确定。分离得到的该结构域由84个残基组成且不含任何含硫氨基酸。它与酿酒酵母的血红素结合域有49个相同残基，与牛微粒体细胞色素b5有28个相同残基。利用最近发表的酿酒酵母黄素细胞色素b2的三维结构[Z - x. Xia，N. Shamala，P. H. Bethge，L. W. Lim，H. D. Bellamy，N. H. Xuong，F. Lederer和F. S. Mathews（1987年）美国国家科学院院刊84，2629 - 2633]，可以看出在可及的血红素边缘附近仅有带正电荷的侧链，该区域唯一的负电荷是血红素丙酸酯的负电荷。根据Salemme关于细胞色素b5/细胞色素c复合物的模型[F. R. Salemme（1976年）分子生物学杂志102，563 - 568]对该结果的意义进行了讨论。
