N-Arylazido-.beta.-alanyl-Nad+, a new nad+ photoaffinity analog. Synthesis and labeling of mitochondrial NADH dehydrogenase
- 30 January 1990
- journal article
- research article
- Published by American Chemical Society (ACS) in Biochemistry
- Vol. 29 (4), 1094-1098
- https://doi.org/10.1021/bi00456a036
Abstract
N-Arylazido-.beta.-alanyl-NAD+ [N3''-O-{3-[4-(4-azido-2-nitrophenyl)amino]propionyl}NAD+] has been prepared by alkaline phosphatase treatment of arylazido-.beta.-alanyl-NADP+ [N3''-O-{3-[N-(4-azido-2-nitrophenyl)amino]propionyl}NADP+]. This NAD+ analogue was found to be a potent competitive inhibitor (Ki = 1.45 .mu.M) with respect to NADH for the purified bovine heart mitochondrial NADH dehydrogenase (EC 1.6.99.3). The enzyme was irreversibly inhibited as well as covalently labeled by this analogue upon photoirradiation. A stoichiometry of 1.15 mol of N-arylazido-.beta.-alanyl-NAD+ bound/mol of enzyme, at 100% inactivation, was determined from incorporation studies using tritium-labeled analogue. Among the three subunits, 0.85 mol of the analogue was bound to the Mr = 51,000 subunit, and each of the two smaller subunits contained 0.15 mol of the analogue when the dehydrogenase was completely inhibited upon photolysis. Both the irreversible inactivation and the covalent incorporation could be prevented by the presence of NADH during photolysis. These results indicate that N-arylazido-.beta.-alanyl-NAD+ is an active-site-directed photoaffinity label for the mitochondrial NADH dehydrogenase, and are further evidence that the Mr = 51,000 subunit contains the NADH binding site. Previous studies using A-arylazido-.beta.-alanyl-NAD+ [A3''-O-{3-[N-(4-azido-2-nitrophenyl)amino]propionyl}NAD+] demonstrated that the NADH binding site is on the Mr = 51,000 subunit [Chen, S., and Guillory, R. J. (1981) J. Biol. Chem. 256, 8318-8323]. Results are also presented to show that N-arylazido-.beta.-alanyl-NAD+ binds the dehydrogenase in a more effective manner than A-arylazido-.beta.-alanyl-NAD+.This publication has 3 references indexed in Scilit:
- EPR studies of iron-sulfur clusters in isolated subunits and subfractions of NADH-ubiquinone oxidoreductase.Journal of Biological Chemistry, 1985
- Studies of the ferricyanide reductase activities of the mitochondrial reduced nicotinamide adenine dinucleotide-ubiquinone reductase (complex I) utilizing arylazido-?-alanyl NAD+ and arylazido-?-alanyl NADP+Journal of Bioenergetics and Biomembranes, 1985
- STUDIES ON ELECTRON TRANSFER SYSTEM .40. PREPARATION AND PROPERTIES OF MITOCHONDRIAL DPNH-COENZYME Q REDUCTASE1962