Structural analysis of zinc-substituted cytochrome c.Qian, C., Yao, Y., Tong, Y., Wang, J., Tang, W.
(2003) J.Biol.Inorg.Chem. 8: 394-400
- PubMed: 12761660
- DOI: 10.1007/s00775-002-0428-1
- PubMed Abstract:
Zinc-substituted cytochrome c has been widely used in studies of protein-protein interactions and photo-induced electron transfer reactions between proteins. However, the coordination geometry of zinc in zinc-substituted cyt c has not yet been determ ...
Zinc-substituted cytochrome c has been widely used in studies of protein-protein interactions and photo-induced electron transfer reactions between proteins. However, the coordination geometry of zinc in zinc-substituted cyt c has not yet been determined; two different opinions about the coordination have been reached. Here the solution structures of zinc-substituted cytochrome c that might be five-coordinated and six-coordinated have been refined separately by using (1)H NMR spectroscopy, and the zinc coordination geometry was determined just by NOE distance constraints. Structural analysis of the energy-minimized average solution structures of both the pentacoordinated and hexacoordinated geometries indicate that that zinc in zinc-substituted cyt c should be bound to both His18 and Met80, which means that the zinc is six-coordinated. RMSD values of the family of 25 six-coordinated structures from the average structure are 0.66+/-0.13 A and 1.09+/-0.16 A for the backbone and all heavy atoms, respectively. A statistical analysis of the structure indicates its satisfactory quality. Comparison of the solution structure of the six-coordinated energy-minimized average structure of zinc-substituted cytochrome c with the solution structure of reduced cytochrome c reveals that for the overall folding the secondary structure elements are very close. The availability of the structure provides for a better understanding of the protein-protein complex and for electron transfer processes between Zn cyt c and other metalloproteins.
State Key Laboratory of Coordination Chemistry, Nanjing University, 210093, Nanjing, PR China.