Mechanical control of ATP synthase function: activation energy difference between tight and loose binding sites.
Despite exhaustive chemical and crystal structure studies, the mechanistic details of how F(o)F(1)-ATP synthase can convert mechanical energy to chemical, producing ATP, are still not fully understood. On the basis of quantum mechanical calculations using a recent high-resolution X-ray structure, we conclude that formation of the P-O bond may be achieved through a transition state (TS) with a planar PO(3)(-) ion. Surprisingly, there is a more than 40 kJ/mol difference between barrier heights of the loose and tight binding sites of the enzyme. This indicates that even a relatively small change in active site conformation, induced by the gamma-subunit rotation, may effectively block the back reaction in beta(TP) and, thus, promote ATP.
Beke-Somfai
Tamás
T
Department of Chemical and Biological Engineering, Physical Chemistry, Chalmers University of Technology, SE-412 96 Göteborg, Sweden. beke@chalmers.se
Lincoln
Per
P
Nordén
Bengt
B
D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D007700:Kinetics; D008958:Models, Molecular; D011487:Protein Conformation; D017510:Protein Folding; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000378:metabolism*; D011789:Quantum Theory; D013816:Thermodynamics
D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases