cDNA clones encoding a novel serine/threonine protein kinase were isolated from human endothelial cell cDNA libraries. The compiled nucleotide sequence is 1757 base pairs in length and contains an open reading frame encoding a 372 amino acid protein, designated C-2k, with a calculated molecular weight of 43 kDa. Sequence analysis indicates that C-2k contains a conserved protein kinase catalytic domain of 308 residues which exhibits its highest sequence identity of 42% to members of the cdc2 kinase family and contains the structural elements characteristic to cdc2-like kinases. C-2k may therefore represent a new member of the cdc2 kinase family.