KINETICS OF RESOLUTION OF COMPLEX-I (REDUCED DIPHOSPHOPYRIDINE NUCLEOTIDE-COENZYME Q REDUCTASE) OF MITOCHONDRIAL ELECTRON TRANSPORT SYSTEM BY CHAOTROPIC AGENTS

Chaotropic agents (NaSCN, NaClO4, guanidine-HCl, and urea) resolve the enzymic assembly of complex I (reduced diphosphopyridine nucleotide-coenzyme Q reductase) resulting in the solubilization of the reduced diphosphopyridine nucleotide dehydrogenase and the iron-sulfur protein of the complex. They also cause the release of these components from the binary I-III complex and electron transport particle. The resolution of complex I is first order with respect to the appearance of soluble reduced diphosphopyridine nucleotide dehydrogenase and highly temperature dependent at low concentrations of chaotropic agents. As in the case of microsomes and other complexes of the respiratory chain, the aerobic resolution of complex I is accompanied by destruction of the iron-sulfur proteins and considerable lipid oxidation. However, under anaerobic conditions the resolution of complex I by chaotropic agents proceeds in the absence of any detectable lipid oxidation or iron-sulfur protein destruction. Reduced diphosphopyridine nucleotide, but not diphosphopyridine nucleotide or reduced triphosphopyridine nucleotide, impedes the chaotropic-induced resolution of complex I, suggesting that the reduced complex has a more stable conformation. © 1969, American Chemical Society. All rights reserved.