Structural energetics of MgADP binding to the isolated beta subunit of F1-ATPase from thermophilic Bacillus PS3.
The energetics of binding of MgADP to the isolated beta subunit of F(1)-ATPase from thermophilic Bacillus (Tbeta) was characterized by high-precision isothermal titration calorimetry. The reaction was enthalpically driven, with a DeltaCp of -36cal(molK)(-1). To gain insight into the molecular basis of this small DeltaCp, we analyzed the changes in accessible surface areas (DeltaASA) between the structures of empty and MgADP-filled beta subunits, extracted from the crystal structure of bovine heart F(1). Consistent with the experimental DeltaCp, the DeltaASA was small (-775A(2)). We used a reported surface area model developed for protein reactions to calculate DeltaCp and DeltaH from DeltaASA, obtaining good agreement with the experimental values. Conversely, using the same model, a DeltaASA of -770A(2) was estimated from experimental DeltaCp and DeltaH for the Tbeta-MgADP complex. Our structural-energetic study indicates that on MgADP binding the isolated Tbeta subunit exhibits intrinsic structural changes similar to those observed in F(1).
Pérez-Hernández
Gerardo
G
Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico.
García-Hernández
Enrique
E
Zubillaga
Rafael A
RA
de Gómez-Puyou
Marietta Tuena
MT
D000244:Adenosine Diphosphate / Q000378:metabolism*; D000818:Animals; D001407:Bacillus / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D002417:Cattle; D008274:Magnesium / Q000378:metabolism*; D008958:Models, Molecular; D011487:Protein Conformation; D021122:Protein Subunits; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D012997:Solvents; D013816:Thermodynamics
D001426:Bacterial Proteins; D021122:Protein Subunits; D012997:Solvents; D000244:Adenosine Diphosphate; D006180:Proton-Translocating ATPases; D008274:Magnesium