Absorption spectra and magnetic circular dichroism of heme-containing proteins in nonequilibrium states. VI. Cytochrome c-oxidase

Low temperature (77 degrees K) absorption spectra of nonequilibrium states of cytochrome c oxidase produced by reduction of oxidases form protein by thermolysed electrons at 77 degrees K was studied. During reduction of cytochrome oxidase water-glycerol solution by thermolysed electrons at 77 degrees K a nonequilibrium reduced protein is formed. Low temperature (77 degrees K) absorption spectra of the nonequilibrium cytochrome oxidase differs from those reduced by ditionite. It was shown that the oxidation state of cytochrome a3 or addition of cytochrom c have no influence on these spectral changes. It is assumed, that the observed effects are conditioned by structural differences of reduced and oxidased cytochrome oxidase active center. Similar spectral changes were observed for cytochrome oxidase, bound to the mitochondrial membrane. At temperature increasing the low temperature reduced protein is relaxed to a corresponding equilibrium state. The spectral properties of bacterial cytochrome oxidase M. lysodeicticus do not depend on the way of reduction (by dytionite or thermolysed electrons at 77 degrees K).