Resolving stepping rotation in Thermus thermophilus H+-ATPase/ synthase with an essentially drag-free probe

Abstract

Vacuole-type ATPases (VoV1) and FoF 1 ATP synthases couple ATP hydrolysis/synthesis in the soluble V 1 or F1 portion with proton (or Na+) flow in the membrane-embedded Vo or Fo portion through rotation of one common shaft. Here we show at submillisecond resolutions the ATP-driven rotation of isolated V1 and the whole VoV1 from Thermus thermophilus, by attaching a 40-nm gold bead for which viscous drag is almost negligible. V1 made 120 ° steps, commensurate with the presence of three catalytic sites. Dwells between the steps involved at least two events other than ATP binding, one likely to be ATP hydrolysis. V oV1 exhibited 12 dwell positions per revolution, consistent with the 12-fold symmetry of the Vo rotor in T. thermophilus. Unlike F 1 that undergoes 80 °-40 ° substepping, chemo-mechanical checkpoints in isolated V1 are all at the ATP-waiting position, and Vo adds further bumps through stator-rotor interactions outside and remote from V1. © 2011 Macmillan Publishers Limited. All rights reserved.