AI Article Synopsis
- The binding of MgADP to the beta subunit of F(1)-ATPase from thermophilic Bacillus was analyzed using isothermal titration calorimetry, revealing the reaction is enthalpically driven.
- A small change in heat capacity (DeltaCp) of -36 cal(molK)(-1) and a minimal change in accessible surface areas (DeltaASA) (-775 A²) were observed during this binding process.
- The findings suggest that the structural changes occurring in the isolated beta subunit upon MgADP binding are similar to those seen in the F(1) complex, demonstrating intrinsic alterations in protein structure during the reaction.
Article Abstract
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).
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| http://dx.doi.org/10.1016/s0003-9861(02)00577-5 | DOI Listing |
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