Molecular Weight of Two States of Cytochrome c Oxidase

This is the authors' abstract. We don't add key points for this paper.

Cytochrome oxidase, as prepared by the Yonetani method, is shown to have a molecular weight of 200,000 (±5%). At alkaline pH (from pH 9.5 to 11, 0.01 m phosphate, 0.1% nonionic detergent) the enzyme dissociates to a monomer species with a molecular weight of 100,000 (±5%). Qualitative results are presented to show that the rate of conversion of dimer to monomer is slow but strongly pH dependent. Between pH 9.5 and 10.5 a mixture of monomer and dimer is obtained when incubation at 4° is relatively short (≤10 hours), but the conversion is essentially complete upon standing at pH 10.5 for 24 hours. Although monomer preparations can be obtained which appear to be mono-disperse from Archibald studies, the dimer isolated at neutral pH contains a small and probably variable amount of the monomer.