Pharmacology. In the article “The pfmdr1 gene of Plasmodium falciparum confers cellular resistance to antimalarial drugs in yeast cells” by Stephan Ruetz, Ulrike Delling, Martine Brault, Erwin Schurr, and Philippe Gros, which appeared in number 18, September 3, 1996, of Proc. Natl. Acad. Sci. USA (93, 9942–9947), the authors wish to note the following:
We have been unable to reproduce complementation of the yeast Saccharomyces cerevisiae ste6 mutant by the Plasmodium falciparum gene pfmdr1 in 400 new yeast transformants tested. Additional studies suggest that the original pfmdr1-associated mating activity was caused by contaminating STE6 sequences that were detected by Southern blotting in frozen vials of pfmdr1 transformants from that period. We have also been unable to isolate new pfmdr1 transformants showing high levels of multidrug resistance. In new pfmdr1 transformants, only resistance to halofantrine was observed. However, this resistance was low, not pleiotropic, and difficult to reproduce systematically. The reason for the discrepancy in drug resistance phenotype of current vs. former pfmdr1 transformants could not be determined with certainty but may reflect a unique population of pfmdr1 transformants available at the time, or a unique set of experimental conditions that could not be recreated. Thus, we are retracting the above manuscript. Contact P. Gros (gros@med.mcgill.ca) should you need additional information or wish to discuss this work further.