Phosphorylation of molluscan paramyosin

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Abstract
InMytilus edulis two proteins of the contractile apparatus can be phosphorylated by cyclic AMP dependent protein kinases: a 295,000 d protein of unknown function, and paramyosin. Paramyosin isolated from thick filaments by the selective extraction method contains the 106,000 d monomer only, whereas paramyosin extracted from ethanol ether dried powder contains equal amounts of the 108,000 d, and the 106,000 d monomers, and traces of the 104,000 d monomer. Paramyosin isolated from ethanol ether dried powder incorporates up to four times the amount of32P than paramyosin isolated by the selective extraction method. Cytoplasmatic protein kinases show a higher affinity towards paramyosin as a phosphoryl acceptor than protein kinases associated with paramyosin. Paramyosin of 5-HT treated catch muscles is phosphorylated 2 to 4 times better than paramyosin of ACh treated or untreated catch muscles.