Abstract: 　Objective To clone and characterize a Rac1 homologue from Trichomonas vaginalis for studying cell cycle of the organism. Methods A cDNA library derived from T. vaginalis mRNA was constructed into λ TriplEx2 phage vector. An expression sequence tag program was launched. Sequences of cDNA clones were analyzed using NCBI BLAST algorithms, and ClustalW and Treeview programs. Results A cDNA clone with a length of 714 base pairs was isolated. The sequence analysis showed that the cDNA clone has an open reading frame with 600 bp. The deduced amino acid sequence from the open reading frame contains 200 residuals and is most homologous to Rac1 subfamily of Rho GTPases with >60% identity. The conserved sequence elements of Rho GTPases, such as GTP binding sites, GTPase activating protein (GAP) interaction motifs, GTP dissociation inhibitors (GDI) interaction motifs, guanine nucleotide exchange factor (GEF) interaction elements, etc, were detected in the amino acid sequence. The phylogenetic analysis showed that the cDNA clone is grouped in the Rac subfamily and is more closely related to Rac1 proteins of protozoa. Conclusion The cDNA clone isolated belongs to Rac subfamily of Rho GTPases and is probably a Rac1 protein of T. vaginalis.

Key words: Trichomonas vaginalis, Rac1 GTPase, cDNA clone