pfmdr2 confers heavy metal resistance to Plasmodium falciparum.
Heavy metals are required by all organisms for normal function, but high levels of heavy metals are toxic. Therefore, homeostasis of these metals is crucial. In the human malaria-causing agent Plasmodium falciparum, the mechanisms of heavy metal transport have yet to be characterized. We have developed a P. falciparum line resistant to heavy metals from a wild-type line sensitive to heavy metals. A molecular and biochemical analysis of the involvement of the P. falciparum multidrug resistance 2 (pfmdr2) gene, an ABC-type transporter, in heavy metal homeostasis was studied. Using a novel uptake assay applied on these two strains, it was demonstrated that, when exposed to heavy metals, the sensitive line accumulates metal, whereas no accumulation was observed in the resistant line. The accumulation occurs within the parasite itself and not in the cytoplasm of the red blood cell. This difference in the accumulation pattern is not a result of amplification of the pfmdr2 gene or of a change in the expression pattern of the gene in the two lines. Sequencing of the gene from both lines revealed a major difference; a stop codon is found in the sensitive line upstream of the normal termination, resulting in a truncated protein that lacks 188 amino acids that contain a portion of the essential cytoplasmatic transporter domain, thereby rendering it inactive. In contrast, the resistant line harbors a full-length, active protein. These findings strongly suggest that the PFMDR2 protein acts as an efflux pump of heavy metals.
Rosenberg
Elli
E
Department of Microbiology and Immunology, Faculty of Health Sciences, Ben-Gurion University of the Negev, 84105 Beer-Sheva, Israel.
Litus
Ilena
I
Schwarzfuchs
Nurit
N
Sinay
Rosa
R
Schlesinger
Pnina
P
Golenser
Jacob
J
Baumeister
Stefan
S
Lingelbach
Klaus
K
Pollack
Yaakov
Y
D000595:Amino Acid Sequence; D000818:Animals; D002104:Cadmium / Q000737:chemistry / Q000378:metabolism; D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism; D004912:Erythrocytes / Q000469:parasitology; D006706:Homeostasis; D006801:Humans; D008969:Molecular Sequence Data; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000502:physiology*; D010963:Plasmodium falciparum / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D002104:Cadmium; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D012333:RNA, Messenger; C513499:Mdr2 protein, Plasmodium falciparum