Trichomonas vaginalis and early evolving DNA and protein sequences of the CDC2/28 protein kinase family.

The human sexually transmitted parasite Trichomonas vaginalis is a representative of one of the three earliest evolving eukaryotic lineages. We investigated whether T. vaginalis has DNA sequences and peptides related to cell division control molecules universal among yeasts and higher eukaryotes. A T. vaginalis cell division control (CDC2/28) homologue was amplified by the polymerase chain reaction and sequenced. The absolute similarity with other CDC2/28 genes was 47%, with conservative replacement similarity of 67%. Western blots demonstrated a single T. vaginalis peptide reactive with antiserum to the PSTAIRE peptide, an expressed component of CDC2/28 genes in higher eukaryotes. Although eukaryotic, T. vaginalis has properties similar to those of bacteria and is the earliest evolving eukaryote reported to possess CDC2/28 DNA and peptide homologues. These observations suggest that the molecular origins of cell division control in eukaryotes preceded mitochondria, 28S ribosomes and regulated glycolysis.