Pause and rotation of F-1-ATPase during catalysis

FI-ATPase is a rotary motor enzyme in which a single ATP molecule drives a 120 degrees rotation of the central gamma subunit relative to the surroundi ng alpha (3)beta (3) ring. Here, we show that the rotation of F-1-ATPase sp ontaneously lapses into long (approximate to 30 s) pauses during steady-sta te catalysis. The effects of ADP-Mg and mutation on the pauses, as well as kinetic comparison with bulk-phase catalysis, strongly indicate that the pa used enzyme corresponds to the inactive state of F-1-ATPase previously know n as the ADP-Mg inhibited form in which F-1-ATPase fails to release ADP-Mg from catalytic sites. The pausing position of the gamma subunit deviates fr om the ATP-waiting position and is most likely the recently found intermedi ate 90 degrees position.