STUDIES ON OXIDATIVE PHOSPHORYLATION .19. FUNCTIONAL SITE OF FACTOR B IN ENERGY TRANSFER REACTIONS

In bovine heart submitochondrial particles exposed to ammonia and ethylenediaminetetraacetate, the ATP-Pi exchange and ATP-driven nicotinamidenucleotide transhydrogenase activities were stimulated by Factor B. These activities were inhibited by p-chloromercuriphenylsulfonate, while the ATPase activity was much less sensitive. The presence of a functionally active -SH in Factor B (shown earlier) and the above results suggest that Factor B may be involved in the formation of a nonphosphorylated high-energy intermediate necessary for the above reactions. A preparation of rabbit serum immune to Factor B gave a single precipitin band with the factor. It also inhibited completely the stimulation of oxidative phosphorylation, ATP-driven NAD reduction by succinate, and ATP-Pi exchange induced by added factor. The same activities, endogenous to a phosphorylating particle, were inhibited only partially by the immune serum, presumably due to inaccessibility of part of the particle-bound Factor B. © 1969.