PMID: 208602Jul 6, 1978

The effect of mitochondrial energization on cytochrome c oxidase kinetics as measured at low temperatures. I. The reaction with carbon monoxide

Biochimica Et Biophysica Acta
H J Harmon, M Sharrock

Abstract

The kinetics of CO binding by the cytochrome c oxidase of pigeon heart mitochondria were studied as a function of membrane energization at temperatures from 180 to 280 degrees K in an ethylene glycol/water medium. Samples energized by ATP showed acceleration of CO binding compared to those untreated or uncoupled by carbonylcyanide p-trifluoromethyoxyphenylhydrazone but only at relatively low temperatures and high CO concentrations. Experiments using samples in a "mixed valency" (partially oxidized) state showed that the acceleration of ligand binding is not due to the formation of a partially oxidized state via reverse electron transport. It is concluded that in the deenergized state one CO molecule can be closely associated with the cytochrome a3 heme site without actually being bound to the heme iron; in the energized state, two or more ligand molecules can occupy this intermediate position. The change in the apparent ligand capacity of a region near the heme iron in response to energization is evidence for an interaction between cytochrome oxidase and the ATPase system. Furthermore, these results suggest a control mechanism for O2 binding.

References

Apr 1, 1975·Proceedings of the National Academy of Sciences of the United States of America·B ChanceJ S Leigh
Oct 31, 1974·Biochimica Et Biophysica Acta·P L Dutton, D F Wilson
Nov 17, 1972·Biochimica Et Biophysica Acta·M K Wikström

Citations

Dec 1, 1988·Journal of Bioenergetics and Biomembranes·H J Harmon
Jan 1, 1988·Bulletin of Environmental Contamination and Toxicology·H J Harmon
Dec 6, 1979·Biochimica Et Biophysica Acta·L C Petersen

Related Concepts

Metazoa
Carbon Monoxide
Cytochrome c Oxidase Subunit VIa
Cytochromes
Energy Metabolism
Melting
Mitochondria, Heart
Columba livia
Plasma Protein Binding Capacity

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