ATP synthase uses a unique rotational mechanism to convert chemical energy into mechanical energy and back into chemical energy. The helix-turn-helix motif termed “DELSEED-loop” in the C-terminal domain of the beta subunit was suggested to be involved in coupling between catalysis and rotation. Here, the role of the DELSEED-loop was investigated by functional analysis of mutants of Bacillus PS3 ATP synthase that had 3 – 7 amino acids within the loop deleted. All mutants were able to catalyze ATP hydrolysis, some at rates several times higher than the wild-type enzyme. In most cases ATP hydrolysis in membrane vesicles generated a transmembrane proton gradient, indicating that hydrolysis occurred via the normal rotational mechanism. Except for two mutants which showed low activity and low abundance in the membrane preparations, the deletion mutants were able to catalyze ATP synthesis. In general, the mutants seemed less well coupled than the wild-type enzyme, to a varying degree.
|Journal||Journal of Biological Chemistry|
|State||Published - Apr 24 2009|