Characterisation of a polo-like protein kinase gene homologue from an evolutionary divergent eukaryote, Trypanosoma brucei.
The polo-like protein kinase gene family (PLKs) encodes proteins which are involved in the control of exit from mitosis in higher eukaryotes. We have cloned and analysed a polo-like kinase, tbplk, from an evolutionary divergent eukaryote, Trypanosoma brucei. The gene encodes a 767 amino acid protein of predicted size 86.8 kDa with 50.4% identity to mammalian PLKs over the protein kinase catalytic domain and it possesses a conserved motif, the 'polo-box', which is found in all PLKs. Phylogenetic analysis demonstrates that this gene is clearly a member of the PLK family, although it has some distinctive features such as a large C-terminal insertion when compared with mammalian PLKs. The gene is single copy and expressed in both bloodstream and procyclic stage trypanosomes. Sequencing of tbplk from a number of trypanosome isolates reveals a length polymorphism in a run of asparagine residues within the coding region. The presence of PLKs in a wide range of organisms, including such a primitive organism as T. brucei, suggests that PLKs may have a key role in the function of the cell cycle.
Graham
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Wellcome Unit of Molecular Parasitology, University of Glasgow, Anderson College, UK.
Tait
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D000595:Amino Acid Sequence; D000818:Animals; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D003001:Cloning, Molecular; D019143:Evolution, Molecular; D017125:Genes, Protozoan; D008969:Molecular Sequence Data; D012150:Polymorphism, Restriction Fragment Length; D011494:Protein Kinases / Q000235:genetics*; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D017422:Sequence Analysis, DNA; D014346:Trypanosoma brucei brucei / Q000235:genetics*; D000097869:Polo-Like Kinase 1
D018797:Cell Cycle Proteins; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D000097869:Polo-Like Kinase 1