Fig. 1.

PKA phosphate transfer energetics depend on protein conformation. (a) Energy along reaction pathway for the 244-atom system in the RC and TC conformers. Reactants (ATP plus protonated serine) are at left. The reaction in RC is extremely unfavorable, whereas the TC conformation allows isoenergetic reactants and products with a barrier of only 12 kJ/mol. (b) Structures for reactants, transition state, and products of calculated phosphate transfer pathway in PKA for a 244-atom TC structure. Note that 1 eV per molecule is 100 kJ/mol.