With the goal of understanding possible mechanisms of drug resistance by the protozoan parasite Entamoeba histolytica (Eh), two novel Eh P-glycoprotein (Pgp) genes (Eh pgp5 and Eh pgp6) were sequenced, and the expression of four Eh pgp genes determined in wild-type (wt) clone A and emetine-resistant (EmR) clone C2 amebae. The Eh pgp5 gene encodes a 1301-amino acid (aa) protein that is similar to those of Eh pgpl (64% aa identity), Eh pgp2 (61%), Eh pgp6 (39%) and Homo sapiens MDR (multidrug-resistance-encoding)(Hs MDR1; 38%) genes. The 1282-aa Eh pgp6 open reading frame (ORF), which is 19-28 aa shorter than those encoded by other Eh pgp, is also similar to those of Eh pgp1 (46% aa identity), Eh pgp2 (38%), and Hs MDR1 (39%). Both Eh pgp5 and Eh pgp6 ORF predict two ATP-binding cassettes and twelve hydrophobic α-helices, which form the putative transmembrane channel. EmRclone C2 amebae, growing at all concentrations of drug, show increased amounts of Eh pgpl and Eh pgp6 mRNA when compared to wt clone A amebae. In contrast, only clone C2 amebae selected for growth at the highest concentrations of emetine (100-200 μg/ml) show increased Eh pgp5 mRNA, while mRNA of both clone C2 and clone A Eh amebae fail to bind an Eh pgp2-specific probe. It appears then that multiple Pgp may contribute to amebic Em resistance in vitro. © 1995.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below