PROTEIN-PHOSPHORYLATION IN THE MOLTING GLAND OF THE CRAYFISH, ORCONECTES-LIMOSUS - ROLE OF CYCLIC-NUCLEOTIDES, CALCIUM, AND MOLT INHIBITINGHORMONE (MIH)

Y-organs of the crayfish Orconectes limosus revealed a phosphorylation pattern which varied in different moulting stages. A 95-kDa-phosphopr otein increased in abundance as moulting proceeded, becoming the predo minant phosphoprotein in stage D-1. Phosphorylation of proteins with a pparent molecular masses of 68 (pp68) and 17 kDa decreased during the moulting cycle. Phosphorylation of pp68 was evoked by incubating Y-org ans of premoult animals with sinus gland extract. The presence of Ca2 induced a decrease in overall kinase activity in Y-organ homogenates and also caused reduced phosphorylation of endogenous Y-organ proteins , most of them (200, 40, 31, and 17 kDa) exhibiting cAMP-dependent pho sphorylation. cAMP-dependent phosphorylation of a 34- and 31-kDa-phosp hoprotein (pp34, pp31) was detectable only in Y-organs of premoult ani mals. A 40-kDa-protein may be a substrate for an endogenous cGMP-depen dent protein kinase since its phosphorylation can be stimulated by cGM P as well as cAMP.