Phosphorylation of brain muscarinic receptor: evidence of receptor regulation

Muscarinic receptor, from porcine synaptic membrane, was purified by affinity chromatography. Molecular weight analysis by SDS-gel electrophoresis revealed one major peptide with an apparent Mr of 68 +/- 2 Kda. The purified receptor was phosphorylated by the catalytic subunit of cAMP-dependent protein kinase resulting in a concomitant loss in specific binding, and this loss was reversed by calcineurin.