  ATP synthases utilize a proton motive force to synthesize ATP. In reverse,
these membrane-embedded enzymes can also hydrolyze ATP to pump protons over the
membrane. To prevent wasteful ATP hydrolysis, distinct control mechanisms exist
for ATP synthases in bacteria, archaea, chloroplasts and mitochondria.
Single-molecule F\"orster resonance energy transfer (smFRET) demonstrated that
the C-terminus of the rotary subunit epsilon in the Escherichia coli enzyme
changes its conformation to block ATP hydrolysis. Previously we investigated
the related conformational changes of subunit F of the A1AO-ATP synthase from
the archaeon Methanosarcina mazei G\"o1. Here, we analyze the lifetimes of
fluorescence donor and acceptor dyes to distinguish between smFRET signals for
conformational changes and potential artefacts.
