title: The antimalarial drug, chloroquine, interacts with lactate dehydrogenase from Plasmodium falciparum.
abstract: We have previously shown that a radioiodinated photoreactive analogue of chloroquine, [125I]N-(4-(4-diethylamino-1-methylbutylamino)quinolin-6-yl) -4-azido-2-hydroxybenzamide ([125I]ASA-Q), specifically labels two proteins in Plasmodium falciparum with apparent molecular weights (Mr) of 42 and 33 kDa (Foley M, Deady LW, Ng K, Cowman AF, Tilley L. J Biol Chem 1994:269:6955-6961). We now report the identification of the 33 kDa protein. The 33 kDa protein was purified from Plasmodium falciparum using photoaffinity labeling with [125I]ASA-Q to monitor the enrichment process. N-terminal sequence analysis of the purified protein revealed exact identity of the first 35 amino acids with P. falciparum lactate dehydrogenase (PfLDH). The plasmodial enzyme was cloned and expressed in E. coli and the recombinant protein used to produce a rabbit antiserum. Immunoprecipitation using affinity-purified anti-PfLDH antibodies confirmed the identity of the 33 kDa CQ-binding protein. The enzyme activity of purified PfLDH was not significantly affected by chloroquine indicating that PfLDH is not a direct target of CQ. PfLDH was, however, shown to be exquisitely sensitive to inhibition by free heme and chloroquine protected against this inhibitory effect.
authors.affiliation: The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.
authors.forename: J G
authors.initials: JG
authors.lastname: Menting
authors.forename: L
authors.initials: L
authors.lastname: Tilley
authors.forename: L W
authors.initials: LW
authors.lastname: Deady
authors.forename: K
authors.initials: K
authors.lastname: Ng
authors.forename: R J
authors.initials: RJ
authors.lastname: Simpson
authors.forename: A F
authors.initials: AF
authors.lastname: Cowman
authors.forename: M
authors.initials: M
authors.lastname: Foley
mesh_terms: D000345:Affinity Labels; D000595:Amino Acid Sequence; D000818:Animals; D000962:Antimalarials / Q000494:pharmacology*; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002738:Chloroquine / Q000494:pharmacology*; D003001:Cloning, Molecular; D004912:Erythrocytes / Q000378:metabolism / Q000469:parasitology; D004926:Escherichia coli / Q000235:genetics; D006427:Hemin / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007770:L-Lactate Dehydrogenase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics; D011485:Protein Binding; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D000345:Affinity Labels; D000962:Antimalarials; D002352:Carrier Proteins; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; D006427:Hemin; D002738:Chloroquine; D007770:L-Lactate Dehydrogenase