The active form of cytochrome c oxidase: effects of detergent, the intact membrane, and radiation inactivation

Journal Article · Fri Jan 01 00:00:00 EST 1982 · Biophys. J.; (United States)

DOI:https://doi.org/10.1016/S0006-3495(82)84677-8· OSTI ID:5705251

Thompson, D A; Suarez-Villafane, M; Ferguson-Miller, S

Cytochrome oxidase is a multisubunit, intrinsic membrane protein with a complex function that includes oxidation of cytochrome c, reduction of oxygen and generation of a membrane potential. To clarify the relationship of its normal function to protein and membrane structure, we have examined the kinetic behavior of rat liver cytochrome oxidase in the intace inner mitochondrial membrane and in detergent solubilized states. Dissolution of rat liver mitochondrial membranes alters the kinetic parameters of the oxidase in a manner dependent in part on the dispersing agent, and characterized by a large increase in maximal activity which is not attributable to exposure of more oxidase or diminished affinity for cytochrome c. The most profound effect of solubilization of the membrane is seen on the low affinity reaction of cytochrome c, suggesting that the electron transfer pathway from this site to oxygen is sensitive to alterations in hydrophobic interactions within the oxidase. Purified rat liver and beef heart oxidase exists predominantly in a monodisperse, 300 kilodalton form in laurylmaltoside (Rosevear et al., 1980). However, a smaller, 130 kd species that exhibits high turnover rates equal to the 300 kd form is detected in some beef heart preparations, implying that the dimer may not be essential for high activity. Radiation inactivation studies on purified oxidase reveal a molecular weight for the functional unit of approx.70 kd. It is concluded that less than a complete set of subunits may be sufficient for both normal bindings of cytochrome c and rapid electron transfer to oxygen.

• Research Organization: Michigan State Univ., East Lansing, MI (United States)
• OSTI ID: 5705251
• Journal Information: Biophys. J.; (United States), Vol. 37:1
• Country of Publication: United States
• Language: English

Related Subjects

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
CYTOCHROME OXIDASE
BIOLOGICAL RADIATION EFFECTS
IRRADIATION
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL FUNCTIONS
COWS
DETERGENTS
HEART
INACTIVATION
LIVER
MEMBRANES
RATS
RESPONSE MODIFYING FACTORS
ADDITIVES
ANIMALS
BIOLOGICAL EFFECTS
BODY
CARDIOVASCULAR SYSTEM
CATTLE
DIGESTIVE SYSTEM
DOMESTIC ANIMALS
EMULSIFIERS
ENZYMES
FUNCTIONS
GLANDS
HAEM DEHYDROGENASES
KINETICS
MAMMALS
ORGANS
OXIDOREDUCTASES
RADIATION EFFECTS
REACTION KINETICS
RODENTS
RUMINANTS
SURFACTANTS
VERTEBRATES
WETTING AGENTS
560111* - Radiation Effects on Biochemicals- In Vitro- (-1987)