title: Purification of a novel isoform of the regulatory subunit of cAMP-dependent protein kinase from the bivalve mollusk Mytilus galloprovincialis.
abstract: Cytosolic extracts from the posterior adductor muscle of the bivalve mollusk Mytilus galloprovincialis contain significant amounts of both cGMP-binding and cGMP-stimulated protein kinase activities. However, photoaffinity labeling with 8-azido-[32P]cGMP revealed only a major cGMP-binding protein with an apparent molecular mass of 54 kDa (p54), lacking protein kinase activity itself. Instead, the purified and cGMP-free p54 protein has the ability to inhibit a mussel protein kinase homologous to the mammalian cAMP-dependent protein kinase (cAPK) catalytic subunit, the inhibition being relieved by cAMP or cGMP, which suggests that it can act as a regulatory subunit of cAPK. However, p54 failed to be recognized by a specific antibody against the regulatory subunit (type RII) previously isolated from mussel. Therefore, p54 must be a novel isoform of cAPK regulatory subunit that seems to have high affinity for both cGMP and cAMP.
authors.affiliation: Faculty of Veterinary, University of Santiago de Compostela, Lugo, 27002, Spain.
authors.forename: J L
authors.initials: JL
authors.lastname: Rodríguez
authors.forename: R
authors.initials: R
authors.lastname: Barcia
authors.forename: J I
authors.initials: JI
authors.lastname: Ramos-Martínez
authors.forename: J A
authors.initials: JA
authors.lastname: Villamarín
mesh_terms: D000818:Animals; D049872:Bivalvia / Q000201:enzymology*; D002352:Carrier Proteins / Q000302:isolation & purification; D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry* / Q000302:isolation & purification*; D006152:Cyclic GMP / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes / Q000737:chemistry* / Q000302:isolation & purification*; D008970:Molecular Weight; D009124:Muscle Proteins / Q000302:isolation & purification / Q000378:metabolism; D009132:Muscles / Q000201:enzymology
chemical_list: D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes; D009124:Muscle Proteins; C022994:cyclic GMP-binding protein; D017868:Cyclic AMP-Dependent Protein Kinases; D006152:Cyclic GMP