A nondiscriminating glutamyl-tRNA synthetase in the plasmodium apicoplast: the first enzyme in an indirect aminoacylation pathway

J Biol Chem. 2013 Nov 8;288(45):32539-32552. doi: 10.1074/jbc.M113.507467. Epub 2013 Sep 26.


The malaria parasite Plasmodium falciparum and related organisms possess a relict plastid known as the apicoplast. Apicoplast protein synthesis is a validated drug target in malaria because antibiotics that inhibit translation in prokaryotes also inhibit apicoplast protein synthesis and are sometimes used for malaria prophylaxis or treatment. We identified components of an indirect aminoacylation pathway for Gln-tRNA(Gln) biosynthesis in Plasmodium that we hypothesized would be essential for apicoplast protein synthesis. Here, we report our characterization of the first enzyme in this pathway, the apicoplast glutamyl-tRNA synthetase (GluRS). We expressed the recombinant P. falciparum enzyme in Escherichia coli, showed that it is nondiscriminating because it glutamylates both apicoplast tRNA(Glu) and tRNA(Gln), determined its kinetic parameters, and demonstrated its inhibition by a known bacterial GluRS inhibitor. We also localized the Plasmodium berghei ortholog to the apicoplast in blood stage parasites but could not delete the PbGluRS gene. These data show that Gln-tRNA(Gln) biosynthesis in the Plasmodium apicoplast proceeds via an essential indirect aminoacylation pathway that is reminiscent of bacteria and plastids.

Keywords: Aminoacyl tRNA Synthetase; Apicoplast; Malaria; Nucleic Acid Enzymology; Plasmodium; Transfer RNA (tRNA).

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apicoplasts / enzymology*
  • Apicoplasts / genetics
  • Glutamate-tRNA Ligase / genetics
  • Glutamate-tRNA Ligase / metabolism*
  • Humans
  • Plasmodium berghei / enzymology*
  • Plasmodium berghei / genetics
  • Plasmodium falciparum / enzymology*
  • Plasmodium falciparum / genetics
  • Protein Biosynthesis / physiology*
  • Protozoan Proteins / genetics
  • Protozoan Proteins / metabolism*
  • RNA, Transfer, Gln / genetics
  • RNA, Transfer, Gln / metabolism
  • RNA, Transfer, Glu / genetics
  • RNA, Transfer, Glu / metabolism
  • Transfer RNA Aminoacylation / physiology*


  • Protozoan Proteins
  • RNA, Transfer, Gln
  • RNA, Transfer, Glu
  • Glutamate-tRNA Ligase