Physico-chemical Properties of Purified Cytochrome a

Abstract

THE enzymatic and spectral properties of purified cytochrome a isolated from animal tissues in soluble form have been studied by many investigators. However, a number of questions remain unanswered as to its physico-chemical properties. In previous communications^1,2 we have reported that a synthetic non-ionic detergent effectively reactivated purified cytochrome a while an ionic detergent was inhibitory. To study cytochrome a in an enzymatically active state in the presence of a non-ionic detergent, we have carried out various sedimentation experiments by ultracentrifuge. The highly purified cytochrome a preparation used in these experiments was prepared from ox heart muscle as described in the previous communication³. Cytochrome a was dialysed against 0.1 M phosphate buffer containing 0.25 per cent ‘Emasol 1130’ at pH 7.4 for 12 hr. The sedimentation pattern of cytochrome a in the presence of the nonionic detergent, ‘Emasol 1130’, showed a single homogeneous and symmetric monodisperse component, as seen in Fig. 1, whereas in the presence of the ionic detergent, sodium cholate, the protein behaved as a polydisperse, aggregated system.