Water may inhibit oxygen binding in hemoprotein models.
Three distal imidazole pickets in a cytochrome c oxidase (CcO) model form a pocket hosting a cluster of water molecules. The cluster makes the ferrous heme low spin, and consequently the O(2) binding slow. The nature of the rigid proximal imidazole tail favors a high spin/low spin cross-over. The O(2) binding rate is enhanced either by removing the water, increasing the hydrophobicity of the gas binding pocket, or inserting a metal ion that coordinates to the 3 distal imidazole pickets.
Collman
James P
JP
Department of Chemistry, Stanford University, Stanford, CA 94305, USA. jpc@stanford.edu
Decréau
Richard A
RA
Dey
Abhishek
A
Yang
Ying
Y
D001665:Binding Sites; D003576:Electron Transport Complex IV / Q000737:chemistry; D006420:Hemeproteins / Q000737:chemistry*; D007093:Imidazoles; D007700:Kinetics; D008670:Metals; D008958:Models, Molecular; D010100:Oxygen / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
D006420:Hemeproteins; D007093:Imidazoles; D008670:Metals; D014867:Water; D003576:Electron Transport Complex IV; D010100:Oxygen