Adenosine 3',5'-monophosphate-receptor protein and protein kinase in Coprinus macrorhizus

A single cAMP-receptor protein could be detected in mycelial extracts of Coprinun macrorhizus by using the photoaffinity cAMP-analogue, 8-N3-cAMP. The protein which specifically bound 32P-labeled 8-N3-cAMP had an apparent molecular weight of 46,000 as determined by an SDS-polyacrylamide gel electrophoresis system. The 46,000-dalton protein was characterized by the dissociation constant for [32P]-8-N3-cAMP, and by the nucleotide specific inhibition of [32P]-8-N3-cAMP binding. The 46,000-dalton protein was co-chromatographed on a DEAE-cellulose column with cAMP-dependent protein kinase. The levels of [32P]-8-N3-cAMP-binding and protein kinase activities in mycelial extracts of strains used was always in parallel. The result indicated that the 46,000-dalton protein may be a regulatory subunit of protein kinase with the capacity to bind cAMP. cAMP-dependent protein kinase of this fungus was immunologically different from those of higher animals.