Fil: Bua, Jacqueline. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Parasitología Dr. Mario Fatala Chaben; Argentina.Fil: Aslund, Lena. Rudbeck Laboratory. Department of Genetics and Pathology; Suecia.Fil: Pereyra, Natalia. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Parasitología Dr. Mario Fatala Chaben; Argentina.Fil: Ruiz, Andrés Mariano. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Parasitología Dr. Mario Fatala Chaben; Argentina.Fil: Bontempi, Esteban J. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Parasitología Dr. Mario Fatala Chaben; Argentina.The immunosuppressive drug cyclosporin A (CsA) has shown antiparasitic activity against several protozoans and helminths, when complexed to proteins called cyclophilins (CyPs). In this paper, the molecular characterisation of one member of the CyP family in Trypanosoma cruzi is reported. TcCyP19 gene proved to be highly conserved compared to CyPs from other organisms and was highly homologous to a Trypanosoma brucei brucei CyPA. This gene was expressed in Escherichia coli and the purified recombinant protein exhibited a peptidyl prolyl cis-trans isomerase activity that was inhibited by CsA (IC(50) = 18.4 + /-0.8 nM). The TcCyP19 gene was located on two chromosomal bands in T. cruzi CL Brener clone.