A single point mutation in the <i>Plasmodium falciparum</i> FtsH1 metalloprotease confers actinonin resistance.

Abstract

The antibiotic actinonin kills malaria parasites (<i>Plasmodium falciparum</i>) by interfering with apicoplast function. Early evidence suggested that actinonin inhibited prokaryote-like post-translational modification in the apicoplast; mimicking its activity against bacteria. However, Amberg Johnson et al. (2017) identified the metalloprotease <i>Tg</i>FtsH1 as the target of actinonin in the related parasite <i>Toxoplasma gondii</i> and implicated <i>P. falciparum</i> FtsH1 as a likely target in malaria parasites. The authors were not, however, able to recover actinonin resistant malaria parasites, leaving the specific target of actinonin uncertain. We generated actinonin resistant <i>P. falciparum</i> by in vitro selection and identified a specific sequence change in <i>Pf</i>FtsH1 associated with resistance. Introduction of this point mutation using CRISPr-Cas9 allelic replacement was sufficient to confer actinonin resistance in <i>P. falciparum</i>. Our data unequivocally identify <i>Pf</i>FtsH1 as the target of actinonin and suggests that actinonin should not be included in the highly valuable collection of 'irresistible' drugs for combatting malaria.