Tyrosine triad at the interface between the Rieske iron-sulfur protein, cytochrome c1 and cytochrome c2 in the bc1 complex of Rhodobacter capsulatus
- 作者：John A. Kyndt ; jkyndt@email.arizona.edu ; John C. Fitch ; Robert E. Berry ; Matt C. Stewart ; Kevin Whitley ; Terry E. Meyer ; F. Ann Walker ; Michael A. Cusanovich1
- 关键词：BC1 ; ubiquinol cytochrome c reductase or Rieske iron&ndash ; sulfur protein/Cytochrome b/Cytochrome c1 complex ; C2 ; cytochrome c2 ; 鈭唂bc ; mutant containing a deletion of the whole BC1 operon ; RCVB ; a minimal growth medium containing mineral salts ; essentia
- 刊名：Biochimica et Biophysica Acta (BBA)/Bioenergetics
- 出版年：2012
- 期刊代码：13_00052728
- 类别：bio
- 出版时间：May, 2012
- 卷：1817
- 期：5
- 页码：811-818
- 文件大小：1104 K
摘要
A triad of tyrosine residues (Y152-154) in the cytochrome c1 subunit (C1) of the Rhodobacter capsulatus cytochrome bc1 complex (BC1) is ideally positioned to interact with cytochrome c2 (C2). Mutational analysis of these three tyrosines showed that, of the three, Y154 is the most important, since its mutation to alanine resulted in significantly reduced levels, destabilization, and inactivation of BC1. A second-site revertant of this mutant that regained photosynthetic capacity was found to have acquired two further mutations鈥擜181T and A200V. The Y152Q mutation did not change the spectral or electrochemical properties of C1, and showed wild-type enzymatic C2 reduction rates, indicating that this mutation did not introduce major structural changes in C1 nor affect overall activity. Mutations Y153Q and Y153A, on the other hand, clearly affect the redox properties of C1 (e.g. by lowering the midpoint potential as much as 117 mV in Y153Q) and the activity by 90%and 50%, respectively. A more conservative Y153F mutant on the other hand, behaves similarly to wild-type. This underscores the importance of an aromatic residue at position Y153, presumably to maintain close packing with P184, which modeling indicates is likely to stabilize the sixth heme ligand conformation.