Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Chemistry and Pharmacology
The X-ray structure of bovine heart cytochrome c oxidase solved for orthorhombic crystals showed a dimeric structure stabilized by four subunit–subunit contacts, namely, subunit Vb–subunit Vb on the matrix side, subunit I–subunit VIa, subunit VIa–subunit I in the transmembrane region and subunit VIb–subunit VIb on the intermembrane side. The same intermonomer contacts as in the orthorhombic crystals were observed in both hexagonal and tetragonal crystals, the X-ray structures of which were determined by the molecular-replacement method. These results suggest that the dimeric structure also exists under physiological conditions. These contacts, especially the subunit IVa–subunit I contact, in which the N-terminal portion of subunit IVa is placed on the surface of subunit I near the dioxygen-reduction site, indicate that the function of the bovine heart enzyme is likely to be controlled by perturbation of the monomer–monomer association.
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