A TRYPANOSOMA-BRUCEI GENE FAMILY ENCODING PROTEIN-KINASES WITH CATALYTIC DOMAINS STRUCTURALLY RELATED TO NEK1 AND NIMA

Using polymerase chain reaction technology we cloned a Trypanosoma brucei gene fragment that has a deduced amino acid sequence with a high degree of homology to protein kinase catalytic domains. This clone detects two genes by genomic Southern analysis. These genes, nrkA and nrkB, share a 97% nt sequence homology over their 1.3-kb coding regions. NrkA encodes a 48-kDa protein which possess all 11 protein kinase homology regions. The 279-aa N-terminal catalytic domain has highest homology with Nek1, a bifunctional kinase, and NIMA, a protein serine/threonine kinase. Both alleles at the nrkB locus in T. brucei strain IsTAR 1 encode a truncated protein kinase catalytic domain due the presence of a premature termination codon. However, the TREU667 strain is heterozygous at the nrkB locus, encoding one truncated and one full-length molecule. NrkA and NrkB possess multiple phosphorylation site motifs. Both nrk transcripts are constitutively expressed during parasite development.