The role of the DELSEED motif of the beta subunit in rotation of F-1-ATPase

F-1-ATPase is a rotary motor protein, and ATP hydrolysis generates torque a t the interface between the gamma subunit, a rotor shaft, and the alpha(3)b eta(3) substructure, a stator ring. The region of conserved acidic "DELSEED " motif of the beta subunit has a contact with gamma subunit and has been a ssumed to be involved in torque generation. Using the thermophilic alpha(3) beta(3)gamma complex in which the corresponding sequence is DELSDED, we rep laced each residue and all five acidic residues in this sequence with alani ne. In addition, each of two conserved residues at the counterpart contact position of gamma subunit was also replaced. Surprisingly, all of these mut ants rotated with as much torque as the wild-type. We conclude that side ch ains of the DELSEED motif of the beta subunit do not have a direct role in torque generation.