The missing link between thermodynamics and structure in F1-ATPase

AUTOR(ES)

Yang, W.

FONTE

The National Academy of Sciences

RESUMO

F1Fo-ATP synthase is the enzyme responsible for most of the ATP synthesis in living systems. The catalytic domain F1 of the F1Fo complex, F1-ATPase, has the ability to hydrolyze ATP. A fundamental problem in the development of a detailed mechanism for this enzyme is that it has not been possible to determine experimentally the relation between the ligand binding affinities measured in solution and the different conformations of the catalytic β subunits (βTP, βDP, βE) observed in the crystal structures of the mitochondrial enzyme, MF1. Using free energy difference simulations for the hydrolysis reaction ATP+H2O → ADP+Pi in the βTP and βDP sites and unisite hydrolysis data, we are able to identify βTP as the “tight” (KD = 10−12 M, MF1) binding site for ATP and βDP as the “loose” site. An energy decomposition analysis demonstrates how certain residues, some of which have been shown to be important in catalysis, modulate the free energy of the hydrolysis reaction in the βTP and βDP sites, even though their structures are very similar. Combined with the recently published simulations of the rotation cycle of F1-ATPase, the present results make possible a consistent description of the binding change mechanism of F1-ATPase at an atomic level of detail.

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