Two yeast genes that encode unusual protein kinases.

Mixed synthetic oligonucleotides encoding sequences conserved among tyrosine-specific protein kinases were used to probe the genome of the budding yeast Saccharomyces cerevisiae. Two genes with homology to protein kinases were isolated and characterized by DNA sequence analysis. These genes, designated KIN1 and KIN2, are closely related to each other. Among previously characterized protein kinases, the products of KIN1 and KIN2 are most closely related to the bovine cAMP-dependent protein kinase (30% amino acid identities) and the protein encoded by the v-src oncogene (27% and 25% identities with KIN1 and KIN2, respectively) within their putative kinase domains. KIN1 and KIN2 are transcribed into 3.5-kilobase mRNAs that contain uninterrupted open reading frames encoding polypeptides of 117 kDa and 126 kDa, respectively. The predicted proteins are unusual in two respects: (i) their catalytic domains are carried near the N termini of relatively large proteins, in contrast to the majority of characterized protein kinases, and (ii) these catalytic domains are structural mosaics, with some features characteristic of tyrosine-specific protein kinases and other elements that are distinctive of serine/threonine-specific enzymes.