Influence of detergent polar and apolar structure upon the temperature dependence of beef heart cytochrome c oxidase activity

Abstract

The temperature dependence of lipid-depleted beef heart cytochrome c oxidase activity was studied in a series of chemically homogeneous detergents. The detergents that were tested included C10 to C18 maltosides, C8 to C12 glucosides, C8 to C16 Zwittergents, and C12 poly(oxyethylene) ethers. The observed rates of electron transport were dependent upon the structure of the polar head group and the length of the hydrocarbon tail. Of the detergents tested, the alkyl maltosides were the best in terms of both high rates of electron transport and superior enzyme stability. With the maltosides, changing the length of the alkyl tail affected the activity of cytochrome c oxidase in a manner quite similar to that reported with synthetic phosphatidylcholines and phosphatidylethanolamines [Vik, S. B., & Capaldi, R. A. (1977) Biochemistry 16, 5755-5759], suggesting that the alkyl maltosides can mimic some of the features of the membrane environment. In each of the detergents, the activation enthalpy (determined from the slope of an Arrhenius plot) was nearly identical, suggesting that the same electron-transfer step within cytochrome c oxidase is rate limiting. This result has been interpreted as evidence for the existence of two or more conformers of cytochrome c oxidase, one of which is significantly more active than the other(s). The enzyme turnover number, which changes by 2 orders of magnitude depending upon the structure of the bound detergent, may reflect the ability of each detergent to alter the equilibrium between the active and nearly inactive conformers.

Cancellation of the cooperativity of Ca2+ binding to sarcoplasmic reticulum Ca2+‐ATPase by the non‐ionic detergent dodecylmaltoside

“…Our suggestion concerning the respective role of the alkyl chain and the polar head group in the perturbation by DM of ATPase is strengthened by data obtained on another membrane protein, cytochrome c oxidase. Alkyl maltosides of different chain lengths were shown to modify cytochrome c oxidase activity in a manner similar to that of synthetic phospholipids of comparable chain lengths (Robinson et al, 1985). In addition, chemical labeling of cytochrome c oxidase also suggested that the maltose head group of DM interacted with the protein more strongly than the alkyl ether headgroup of Triton X-100, chemically similar to that of C,,E, (Estey et al, 1990).…”

“…For instance, extensive comparative studies showed DM to be superior to all other detergents tested for the purification and the maintenance of the native structure of soluble cytochrome c oxidase (e.g. Rosevear et al, 1980;Robinson et al, 1985). It has also been used for the purification of a photosystem I1 core complex from spinach (Bricker et al, 1985) and from algae (de Vitry et al…”

Inhibition of membrane‐bound cytochrome c oxidase by zinc ions: High‐affinity Zn2+‐binding site at the P‐side of the membrane

“…COX was isolated from bovine heart essentially as described in [22] (a modified Fowler‐type preparation) according to a protocol kindly provided by Dr. A. Musatov (Department of Biochemistry, UTHSC, San Antonio). The enzyme was reconstituted in egg lecithin vesicles by cholate dialysis method [23].…”

Ferricytochrome c protects mitochondrial cytochrome c oxidase against hydrogen peroxide-induced oxidative damage

“…Preparation A involves sodium cholate solubilization of sodium deoxycholate treated Keilin-Hartree heart muscle particles followed by purification of CcO by ammonium sulfate precipitation as previously described [29]. The resulting purified enzyme was dissolved at ~100 µM in pH 7.4 buffer containing 25 mM sodium cholate and stored at −60 °C.…”