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Identification of multiple isoforms of the cAMP‐dependent protein kinase catalytic subunit in the bivalve mollusc Mytilus galloprovincialis
Author(s) -
Bardales José R.,
Hellman Ulf,
Villamarín J. A.
Publication year - 2008
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2008.06591.x
Subject(s) - protein subunit , gene isoform , mytilus , biology , biochemistry , isozyme , mussel , threonine , protein kinase a , serine , molecular mass , microbiology and biotechnology , kinase , phosphorylation , enzyme , gene , fishery
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 Cα‐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.