MECHANISM OF REGULATION OF cAMP-DEPENDENT PROTEIN KINASE I, A NEW TYPE OF ALLOSTERIC ENZYME CONTROL

Publisher Summary This chapter describes the mechanism of regulation of cAMP-dependent protein kinase I, a new type of allosteric enzyme control. Binding of cAMP to the holoenzyme in the model has to occur with reduced affinity. Evidence suggests that cAMP indeed binds to RC units. ESR spectra of spin-labeled cAMP bound to the enzyme in the presence of ATP proved to be different from those without ATP. The spin label attached to of cAMP was strongly frozen in conditions when the enzyme dissociates, whereas a significantly higher mobility in the presence of ATP was found. Affinity chromatography also showed that R 2 is strongly immobilized, when cAMP is covalently joined to Sepharose through a long spacer, and cannot be detached by free cAMP. ATP and the presence of C lead to detachment and ATP promotes the formation of the holoenzyme, which interacts with reduced affinity with cAMP. Interaction of cAMP with R 2 C 2 was also indicated with experiments that determined the simultaneous binding of ATP and cAMP.