Identification of the catalytic subunit of cAMP-dependent protein kinase from the photosynthetic flagellate, Euglena gracilis Z.
A gene named epk2 that encodes the amino acid sequence of a protein kinase was identified from the photosynthetic flagellate, Euglena gracilis Z. Homology search and phylogenetic analysis revealed that the deduced amino acid sequence of epk2 is most similar to that of the catalytic subunit of cAMP-dependent protein kinase (PKA). Northern blot analysis showed that Euglena cells express a 1.4-kb transcript of this gene. When the EPK2 protein was coexpressed with the rat regulatory subunit of PKA in cultured mammalian cells, these two proteins were coimmunoprecipitated. The association of EPK2 and the rat regulatory subunit of PKA was not detected in the cell lysate incubated with cAMP. EPK2 immunoprecipitated from the transfected cells phosphorylated Kemptide, a synthetic peptide substrate for PKA, and the phosphorylation was inhibited by PKI, a PKA-selective protein kinase inhibitor. These results indicate that EPK2 is a PKA homologue in the photosynthetic flagellate, and this is the first evidence for the occurrence of the PKA catalytic subunit in photosynthetic organisms.
Kiriyama
H
H
Graduate School of Science and Technology, Division of Molecular Science, Kobe University, Japan.
Nanmori
T
T
Hari
K
K
Matsuoka
D
D
Fukami
Y
Y
Kikkawa
U
U
Yasuda
T
T
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D003001:Cloning, Molecular; D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005056:Euglena gracilis / Q000201:enzymology*; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000378:metabolism; D010766:Phosphorylation; D010788:Photosynthesis; D010802:Phylogeny; D011233:Precipitin Tests; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017386:Sequence Homology, Amino Acid; D014162:Transfection
D004791:Enzyme Inhibitors; D009842:Oligopeptides; D015800:Protozoan Proteins; D012333:RNA, Messenger; C037642:kemptide; D017868:Cyclic AMP-Dependent Protein Kinases; C119431:EPK2 protein, Euglena gracilis