Organization of oligomycin-sensitive adenosine triphosphatase.

superaggregates to an active tetramer of 360000daltons and a slow phase of half-time 15s representing the subsequent dissociation of tetramer to an inactive dimer. When enzyme at the same concentration is mixed with 5m-ATP, only the rapid phase of tetramer production is observed. Although it is well known that phosphofructokinase is strongly inhibited by ATP at pH6.8 and that the effect of citrate is apparently synergistic, these light-scattering studies show that the mechanism for inhibition by citrate is different from that by ATP. The dissociation of tetramer by citrate may be reversed by ATP, fructose 6-phosphate and fructose 1,dbisphosphate. Studies at low enzyme concentration reveal that the conformational change induced by ATP before dissociation is not a simple one-step mechanism.