Professor Robert H. Fillingame
University of Wisconsin Medical School
Madison, Wisconsin

Monday, December 11, 2000
3:00 pm (CT)
3269 Beckman Institute

Abstract

ATP is synthesized during oxidative phosphorylation by proton transport coupled rotary catalysis in the F1Fo ATP synthase. Proton transport through the transmembrane Fo sector is coupled to rotation of subunit g within the F1 sector of the enzyme at the periphery of the membrane. An oligomeric ring of 10-12 c subunits provide the proton binding sites, which become alternately accessible to channels from the two sides of the membrane as the ring turns in a 10-12 step fashion. Proton transport occurs at the interface between a single copy of subunit a and the rotating ring of subunit c. In this talk, I will focus on the organization of subunits in the Fo sector of the enzyme and the structural relationship to models of rotary catalysis. A model of the c oligomer has been built based upon the NMR structure of monomeric subunit c and cross-linking distance constraints between the two helices of neighboring subunits. The model predicts that transmembrane helices at the periphery of the c-ring must rotate in order to expose the proton-binding carboxylate of residue cAsp61 to the alternate access channels in subunit a. The proposed turning of helices would also explain the cross-linking pattern observed between subunits a and c. The proton-transport driven rotation of helices is proposed to drive the stepwise movement of the c-ring and ultimately the turning of the g subunit within F1.

Tea and coffee will be served in R3151 Beckman Institute at 2:15pm.