Primary sequences of two P-glycoprotein genes of Entamoeba histolytica.
Two P-glycoprotein genes (EhPgp1 and EhPgp2) from the protozoan parasite Entamoeba histolytica were sequenced from a genomic library made with the DNA of an emetine-resistant ameba mutant, which overexpresses mRNAs homologous to segments of the human mdr1 (P-glycoprotein) gene. The open reading frames for EhPgp1 and EhPgp2 were 1302 and 1310 amino acids long, respectively, and showed a 67% positional identity with each other and 41% and 40% positional identities, respectively, with human mdr1 gene. Within each ameba P-glycoprotein were the ATP-binding sites found twice in eukaryotic P-glycoproteins and once in prokaryotic transport proteins. Hydropathy plots of the ameba P-glycoproteins were nearly superimposable on that of the human mdr 1, showing 2 homologous halves, each containing an ATP-binding site and 6 hydrophobic transmembrane domains that form the putative channel. A phylogenetic tree showed that the Entamoeba P-glycoproteins are more related to the human and mouse P-glycoproteins than to the Plasmodium and Leishmania P-glycoproteins. Also identified in the E. histolytica genomic library were 2 P-glycoprotein pseudogenes, each with a frame shift and stop codons in identical places within the amino ATP-binding site. In conclusion, the 2 E. histolytica P-glycoproteins encoded by the EhPgp1 and EhPgp2 genes are similar in structure to the mammalian P-glycoproteins and so may be involved in energy-dependent drug efflux by this human parasite.
Department of Tropical Public Health, Harvard School of Public Health, Boston, MA 02115.
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S
Descoteaux
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Ayala
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Orozco
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Samuelson
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004748:Entamoeba histolytica / Q000235:genetics*; D017125:Genes, Protozoan / Q000235:genetics*; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D010802:Phylogeny; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics*
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D008562:Membrane Glycoproteins; D015800:Protozoan Proteins