Haemonchus contortus: Sequence heterogeneity of internucleotide binding domains from P-glycoproteins and an association with avermectin/milbemycin resistance

P-Glycoproteins are transmembrane proteins associated with acquired multidr ug resistance in mammalian cells and some protozoan parasites by a process of active drug export. P-glycoproteins contain two nucleotide binding domai ns which couple ATP to the drug transport process. The region between the n ucleotide binding domains of P-glycoproteins, termed the internucleotide bi nding domain (IBD), was PCR-amplified from adult and larval cDNA libraries using degenerate primers. The 11 clones isolated by this method fall into s everal distinct groups, with one group of alleles displaying between 82 and 99% identity at cole nucleotide level. This sets a baseline for sequence v ariation of transcribed alleles from a parasitic nematode, Northern blottin g showed that P-glycoprotein genes are transcribed in a developmentally reg ulated fashion in Haemonchus contortus. Southern blots of H. contortus drug -resistant isolates with an IBD probe revealed a pattern consistent with th e involvement of P-glycoprotein in resistance to avermectin/milbemycin anth elmintics, (C) 1999 Academic Press.