Chen L, Mathews F S, Davidson V L, Tegoni M, Rivetti C, Rossi G L
Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110.
Protein Sci. 1993 Feb;2(2):147-54. doi: 10.1002/pro.5560020203.
A ternary electron transfer protein complex has been crystallized and a preliminary structure investigation has been carried out. The complex is composed of a quinoprotein, methylamine dehydrogenase (MADH), a blue copper protein, amicyanin, and a c-type cytochrome (c551i). All three proteins were isolated from Paracoccus denitrificans. The crystals of the complex are orthorhombic, space group C222(1) with cell dimensions a = 148.81 A, b = 68.85 A, and c = 187.18 A. Two types of isomorphous crystals were prepared: one using native amicyanin and the other copper-free apo-amicyanin. The diffraction data were collected at 2.75 A resolution from the former and at 2.4 A resolution from the latter. The location of the MADH portion was determined by molecular replacement. The copper site of the amicyanin molecule was located in an isomorphous difference Fourier while the iron site of the cytochrome was found in an anomalous difference Fourier. The MADH from P. denitrificans (PD-MADH) is an H2L2 hetero-tetramer with the H subunit containing 373 residues and the L subunit 131 residues, the latter containing a novel redox cofactor, tryptophan tryptophylquinone (TTQ). The amicyanin of P. denitrificans contains 105 residues and the cytochrome c551i contains 155 residues. The ternary complex consists of one MADH tetramer with two molecules of amicyanin and two of c551i, forming a hetero-octamer; the octamer is located on a crystallographic diad. The relative positions of the three redox centers--i.e., the TTQ of MADH, the copper of amicyanin, and the heme group of c55li--are presented.
一种三元电子转移蛋白复合物已被结晶，并进行了初步的结构研究。该复合物由一种醌蛋白、甲胺脱氢酶（MADH）、一种蓝色铜蛋白、氨氰蛋白和一种c型细胞色素（c551i）组成。所有这三种蛋白质均从反硝化副球菌中分离得到。该复合物的晶体为正交晶系，空间群为C222(1)，晶胞参数a = 148.81 Å，b = 68.85 Å，c = 187.18 Å。制备了两种同晶型晶体：一种使用天然氨氰蛋白，另一种使用无铜的脱辅基氨氰蛋白。从前一种晶体收集到分辨率为2.75 Å的衍射数据，从后一种晶体收集到分辨率为2.4 Å的衍射数据。MADH部分的位置通过分子置换确定。氨氰蛋白分子的铜位点在同晶型差值傅里叶图中定位，而细胞色素的铁位点在反常差值傅里叶图中找到。来自反硝化副球菌的MADH（PD-MADH）是一种H2L2异源四聚体，H亚基含有373个残基，L亚基含有131个残基，后者含有一种新型氧化还原辅因子，色氨酸 - 色氨酸醌（TTQ）。反硝化副球菌的氨氰蛋白含有105个残基，细胞色素c551i含有155个残基。三元复合物由一个MADH四聚体与两个氨氰蛋白分子和两个c551i分子组成，形成一个异源八聚体；该八聚体位于一个晶体学二次轴上。给出了三个氧化还原中心的相对位置，即MADH的TTQ、氨氰蛋白的铜和c551i的血红素基团。
