Chemical labeling studies on bovine heart mitocondrial cytochrome c oxidase dispersed in nonionic detergents

• Published in: Biochemistry (Easton) Vol. 29:41
• Main Authors: Estey, L.A., Lincoln, A.J., Prochaska, L.J.
• Format: Journal Article
• Language: English
• Published: United States 01-10-1990
• Subjects: 550201 - Biochemistry- Tracer Techniques; ADDITIVES; ANIMALS; BASIC BIOLOGICAL SCIENCES; BETA DECAY RADIOISOTOPES; BETA-MINUS DECAY RADIOISOTOPES; BODY; CARDIOVASCULAR SYSTEM; CATTLE; CELL CONSTITUENTS; CELL MEMBRANES; CYTOCHROME OXIDASE; DAYS LIVING RADIOISOTOPES; DETERGENTS; DOMESTIC ANIMALS; ELECTRON TRANSFER; ELECTROPHORESIS; EMULSIFIERS; ENZYMES; EVEN-ODD NUCLEI; HAEM DEHYDROGENASES; HEART; ISOTOPE APPLICATIONS; ISOTOPES; LABELLED POOL TECHNIQUES; LABELLING; LIGHT NUCLEI; MAMMALS; MEMBRANES; MITOCHONDRIA; NUCLEI; ORGANOIDS; ORGANS; OXIDOREDUCTASES; RADIOISOTOPES; REAGENTS; RUMINANTS; SULFUR 35; SULFUR ISOTOPES; SURFACTANTS; TRACER TECHNIQUES; VERTEBRATES; WETTING AGENTS
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00493a029

In order to investigate the structural interaction of nonionic detergents with bovine heart mitochondrial cytochrome c oxidase (COX), a series of hydrophilic chemical modification reagents were used to map regions on COX which are not shielded by dodecyl {beta}-D-maltoside (DM), Triton X-100 (TX-100), and Tween 80 (TW-80). Low levels of incorporation of the chemical reagents ({sup 35}S)benzenediazoniumsulfonate (DABS) and N-succinimidyl ({sup 3}H)propionate (SP) into COX dispersed in TW-80 indicate that the bulky headgroup and hydrophobic moiety of this detergent effectively shield the enzyme from the aqueous environment. Subunits II and Va/Vb show an increased reactivity to ({sup 35}S)DABS and ({sup 3}H)SP in TW-80 and may reflect an increased exposure of these subunits to aqueous phase in comparison to COX dispersed in TX-100 or DM. While COX in TX-100 is more reactive with ({sup 3}H)SP than DM-dispersed enzyme, there is no difference in the distribution of label (either DABS or SP) within the subunits of COX in DM or TX-100. These results suggest that the maltose headgroup of DM interacts with COX more strongly than the alkyl ether headgroup of TX-100, with the TX-100-COX interactions stabilized by the short, bulky hydrophobic tail of the detergent. In the absence of favorable headgroup interaction, COX dispersed in TX-100 exhibits lower electron-transfer activity.