Localization of donor and acceptor sites of NADH dehydrogenase activities using inside‐out and right‐side‐out plasma membrane vesicles from plants

Inside‐out and right‐side‐out plasma membrane vesicles from sugar beet (Beta vulgaris L.) leaves, prepared by aqueous two‐phase partitioning, were used to localize donor and acceptor sites and to determine substrate affinities for plasma membrane‐bound NADH dehydrogenase activities. NADH‐ferricyanide and NADH‐cytochrome c reductase activities were approx. 30% latent with inside‐out vesicles and about 80% latent with right‐side‐out vesicles, indicating that both donor and acceptor sites for these activities are located on the cytoplasmic surface of the plasma membrane, and that a possible transplasma membrane electron transport would constitute only a minor proportion of the total activity.