Comparison of NADH-linked cytochrome c reductases of endoplasmic reticulum, golgi aparatus and plasma membrane

Abstract

1. 1. Highly purified rat liver Golgi apparatus (GA) and plasma membranes (PM) fractions exhibited specific NADH-cytochrome c reductase activities of 25 and 10% ofthose found in endoplasmic reticulum (ER), respectively. 2. 2. With ferricyanide as the electron acceptor, the reductase activities of ER, GA and PM exhibited indistinguishable kinetic constants. 3. 3. The activities of NADH-cytochrome c reductase of ER, GA and PM fractions were insensitive to inhibitors of mitochondrial respiration but exhibited differing sensitivities to p-hydroxymercuribenzoate. NADH-ferricyanide reductase activities were stimulated by Triton X-100 and sodium deoxycholate and were insensitive to trypsin, while these agents inactivated the corresponding NADH-cytochrome c reductase activities. 4. 4. NADH-MTT tetrazolium [3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl tetrazolium bromide] reductases of ER, GA and PM were resolved upon polyacrylamide gel electrophoresis into two bands of similar electrophoretic mobility in each of the three fractions. Band II predominated in ER while band I increased in relative abundance in GA and, especially, PM. 5. 5. The findings suggest that ER, GA and PM of rat liver contain NADH dehydrogenases one or more of which may be similar to each other and support the hypothesis that at least one NADH-dehydrogenase complex is common to the three types of membranes (ER, GA and PM). The NADH dehydrogenase complexes of the three fractions were kinetically indistinguishable but other properties of the NADH dehydrogenases of GA were intermediate between those of ER and PM.