Cdc2 proteins are well characterized as protein kinases and are functionally involved in the control of the G2 to M transition during cell division. cdc2 proteins (cdc2Sp, CDC28 and CDC2Gg) and proteins sharing a high degree of similarity with cdc2 proteins (EG1 and DM2C), and therefore belonging to the same structural family, were analyzed using Fourier transform of the coded sequences. Characteristic code/frequency pairs (0.140, 0.148 and 0.238) distinguish the cdc2 proteins from the related proteins. The frequencies 0.140, 0.148 and 0.238 (and the associated codes) allow discrimination between all cdc2 proteins (cdc2Sp, CDC28, CDC2Gg, CDC2Hs, CDC2Mm, CDC2Dm, CDC2Ms) and related proteins (EG1, DM2C, MO15, GTA, PHO85, KSS1, PSKJ3, FUS3, KIN28), thus providing the first evidence for predicting cdc2 function from a sequence. A rice cdc2 homolog (R2) did not match the cdc2 proteins and is, therefore, unlikely to be a cdc2 protein. Pertinent patterns in the cdc2 proteins were searched, and mapped to the 90-210 region (numbering from cdc2 of S. pombe) which correlates well with the putative cyclin binding domain of the cdc2 proteins.