Inhibition and release of respiration in particles from Alcaligenes faecalis

Oxidation of DPNH by phosphorylating particles from Alcaligenes faecalis is stimulated by P i and to a further variable degree by ADP plus P i . The rates of oxidation in the presence and absence of P i and ADP show different pH dependences. When a protein necessary for coupling phosphorylation to electron transport is removed from the particles, respiration is rapid and P i and ADP have no further effect. When this coupling protein (which is also found associated with DPN as an intermediate) is rebound to the particles by magnesium ions and a specific oligoribonucleotide, respiration is slowed, and can again be stimulated or released by P i or P i and ADP. The magnitude of respiratory stimulation by P i or P i and ADP is much smaller that that observed with intact mitochondria, but is similar to that observed with mitochondrial particles. These observations are compatible with our previously stated hypothesis that oxidative phosphorylation is mediated by electron carrier-coupling enzyme intermediates. The stimulating effect of P i or P i and ADP on respiration appears in this system to be the result of releasing electron carriers from such intermediates and thus allowing them to function again in electron transport.