Substrate positions and induced-fit in crystalline adenylate kinase.

The binding positions of ATP and AMP in pig muscle adenylate kinase (EC 2.7.4.3) have been located by X-ray diffraction analysis. For this purpose crystals have been soaked with solutions containing substrates and substrate analogues. Two adenosine pockets and the region of the phosphates have been identified. In combination with other experimental data the pockets have been assigned to the AMP site and the ATP site, respectively. Moreover, the results suggest that the known conformations of adenylate kinase reflect an induced-fit of the enzyme: conformation B being related to the free enzyme E and conformation A being related to E¹, the enzyme species after a substrate-induced conformational change.