Immunochemical studies on function of NADH: hemeprotein oxidoreductase in electron transport system of chromatophores from Rhodospirillum rubrum.

Abstract

An antiserum against NADH: hemeprotein oxidoreductase [EC 1.6.99.3] was obtained by injection into rabbits of the enzyme purified from extracts of whole cells of Rhodospirillum rubrum. With the use of the antiserum, the functional role of the enzyme in the electron transport system of chromatophores was studied. The activities for NADH-cytochrome c2 reduction of chromatophores and pure preparations of the enzyme were approximately 50% inhibited in the presence of the antiserum; in the case with the enzyme, approximately 50% of the enzyme formed insoluble complex with the antiserum. With chromatophores, the antiserum inhibited also the activity for succinate-NAD+ reduction driven by either ATP or light and the activity for NADH-induced photosynthetic ATP formation. To the contrary, it did not influence the activity for succinate-cytochrome c2 reduction and the activities for photosynthetic ATP formation induced by ascorbate, succinate, and phenazine metho-sulfate. On the basis of these findings, it was concluded that the chromatophore membrane contained the same NADH: hemeprotein oxidoreductase as the purified enzyme, and that the bound enzyme was functional in donation of electrons from NADH to the photosynthetic, cyclic electron transport system.