A novel protein kinase from the ciliate Euplotes raikovi with close structural identity to the mammalian intestinal and male-germ cell kinases: characterization and functional implications in the autocrine pheromone signaling loop.
In the free-living ciliate Euplotes raikovi, we identified (and designated as Er-MAPK1) a protein kinase of 631 amino acids, that appears to be constantly phosphorylated in cells which are in growth stage and interact in autocrine fashion with their water-soluble signal pheromones. Er-MAPK1 is specified by a gene that requires a+1 translational frame-shift to be expressed. Its amino-terminal region represents a canonical catalytic domain and carries an activation loop distinctive of the mitogen-activated protein kinases, with the Thr-Asp-Tyr motif deputed to be site of double phosphorylation. In contrast, the carboxy-terminal region appears to be structurally unique. It shows a strongly basic amino acid composition, is very rich in glycine repetitions, and contains a bipartite signal for translocation of Er-MAPK1 into the nucleus.
Vallesi
Adriana
A
Dipartimento di Scienze Ambientali e Naturali, University of Camerino, via Gentile III da Varano, 62032 Camerino (MC), Italy. adriana.vallesi@unicam.it
Di Pretoro
Barbara
B
Ballarini
Patrizia
P
Apone
Fabio
F
Luporini
Pierangelo
P
D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D020134:Catalytic Domain; D016812:Euplotes / Q000201:enzymology* / Q000502:physiology*; D018965:Frameshifting, Ribosomal; D008297:Male; D008969:Molecular Sequence Data; D010675:Pheromones / Q000378:metabolism*; D010802:Phylogeny; D011485:Protein Binding; D014176:Protein Biosynthesis; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism*; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
D010675:Pheromones; D021382:Protein Sorting Signals; D015800:Protozoan Proteins; D011494:Protein Kinases