title: Identification of multiple isoforms of the cAMP-dependent protein kinase catalytic subunit in the bivalve mollusc Mytilus galloprovincialis.
abstract: Several isoforms of the cAMP-dependent protein kinase catalytic subunit (C-subunit) were separated from the posterior adductor muscle and the mantle tissues of the sea mussel Mytilus galloprovincialis by cation exchange chromatography, and identified by: (a) protein kinase activity; (b) antibody recognition; and (c) peptide mass fingerprinting. Some of the isozymes seemed to be tissue-specific, and all them were phosphorylated at serine and threonine residues and showed slight but significant differences in their apparent molecular mass values, which ranged from 41.3 to 44.5 kDa. The results from the MS analysis suggest that at least some of the mussel C-subunit isoforms arise as a result of alternative splicing events. Furthermore, several peptide sequences from mussel C-subunits, determined by de novo sequencing, showed a high degree of homology with the mammalian Calpha-isoform, and contained some structural motifs that are essential for catalytic function. On the other hand, no significant differences were observed in the kinetic parameters of C-subunit isoforms, determined by using synthetic peptides as substrate and inhibitor. However, the C-subunit isoforms separated from the mantle tissue differed in their ability to phosphorylate in vitro some proteins present in a mantle extract.
authors.affiliation: Departamento de Bioquímica e Bioloxía Molecular, Facultade de Veterinaria, Universidade de Santiago de Compostela, Lugo, Spain.
authors.forename: José R
authors.initials: JR
authors.lastname: Bardales
authors.forename: Ulf
authors.initials: U
authors.lastname: Hellman
authors.forename: J A
authors.initials: JA
authors.lastname: Villamarín
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D054751:Cyclic AMP-Dependent Protein Kinase Catalytic Subunits / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D049878:Mytilus / Q000201:enzymology*; D010449:Peptide Mapping; D010766:Phosphorylation; D020033:Protein Isoforms / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D020033:Protein Isoforms; D011506:Proteins; D054751:Cyclic AMP-Dependent Protein Kinase Catalytic Subunits