Adenosine 3', 5'-Monophosphate-Receptor Protein and Protein Kinase in Coprinus macrorhizus

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Abstract
A single cAMP-rcceptor protein could be detected in mycelial extracts of Coprinus 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 elctrophoresis 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.