Regensburg 2004 – scientific programme
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SYLS: Life Sciences on the Nanometer Scale - Physics Meets Biology
SYLS 5: Symposium "Life Sciences on the Nanometer Scale - Physics Meets Biology"
SYLS 5.3: Talk
Thursday, March 11, 2004, 12:00–12:15, H 37
Molecular dynamics simulations of isolated β-subunits of F1-ATPase — •U. Kleinekathöfer1, B. Isralewitz2, M. Dittrich2, and K. Schulten2 — 1International University Bremen, 28725 Bremen — 2Beckman Institute, University of Illinois, Urbana-Champaign, USA.
The F1 unit of ATPase has three-fold symmetry and consists of three noncatalytic α and three catalytic β-subunits. The β-subunits furnish the binding sites where ADP is transformed into ATP. We have investigated the properties of isolated β-subunits as a step towards explaining the function of the integral F1 unit. The β-subunits exist in different conformations at any moment of the F1 unit reaction cycle.
The open conformation of the AlF3-inhibited β-subunit of bovine ATPase had been equilibrated for about 10 ns and a spontaneous change in conformation was observed. The change can be decomposed into two rotations: one around an axis parallel to the pseudo-symmetry axis of F1-ATPase and one around an axis perpendicular to the first axis . In several runs the equilibrated subunit was in a conformation about half-way between the open and the closed conformation. This partially confirms the assumption that elastic energy is stored in the open confirmation. It is unclear if there is a further spontaneous closing motion on longer time scales. To test the effect of the adjacent alpha subunit we performed simulations of the joined units and found only a negligible effect. We also equilibrated isolated β-subunits for the AlF4−-inhibited F1-ATPase starting from the the half-closed state with ADP bound and from modified half-closed states with bound ATP. The simulations again revealed spontaneous motion towards the closed conformation.