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Redox-coupled crystal structural changes in bovine heart cytochrome c oxidase
S Yoshikawa1, K Shinzawa-Itoh, R Nakashima
1Department of Life Science, Himeji Institute of Technology and CREST, Japan Science and Technology Corporation (JST), Kamigohri Akoh, Hyogo 678-1297, Japan.
Science (New York, N.Y.)
|June 20, 1998
Summary
Bovine heart cytochrome c oxidase structures reveal a proton pumping mechanism involving aspartate movement and a tyrosine-imidazole proton donor system for oxygen reduction.
Area of Science:
- Biochemistry
- Structural Biology
- Bioenergetics
Background:
- Cytochrome c oxidase (CcO) is a crucial enzyme in cellular respiration, catalyzing the final step of electron transfer to oxygen.
- Understanding the structural basis of proton pumping in CcO is essential for elucidating energy transduction mechanisms.
Purpose of the Study:
- To determine the high-resolution crystal structures of bovine heart CcO in various functional states.
- To elucidate the structural mechanisms underlying proton pumping and oxygen reduction.
Main Methods:
- X-ray crystallography was employed to obtain crystal structures of bovine heart CcO.
- Structures were determined at high resolution (2.30-2.90 angstroms) in oxidized, reduced, azide-bound, and carbon monoxide-bound states.
Main Results:
- Structural analysis revealed an aspartate residue that changes accessibility between matrix and cytosolic phases upon metal site reduction, identifying it as a proton pumping site.
- A tyrosine residue, acidified by an imidazole nitrogen, was identified as a potential proton donor for oxygen reduction.
Conclusions:
- The study provides key structural insights into the proton translocation mechanism of cytochrome c oxidase.
- The findings highlight the roles of specific amino acid residues in the enzyme's catalytic and proton pumping functions.