Structural basis for the efficient phosphorylation of AZT-MP (3 '-azido-3 '-deoxythymidine monophosphate) and dGMP by Plasmodium falciparum type I thymidylate kinase

Jean L. Whittingham, Juana Carrero-Lerida, James A. Brannigan, Luis M. Ruiz-Perez, Ana P. G. Silva, Mark J. Fogg, Anthony J. Wilkinson, Ian H. Gilbert, Keith S. Wilson, Dolores Gonzalez-Pacanowska

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Plasmodium falciparum is the causative agent of malaria, a disease where new drug targets are required due to increasing resistance to current anti-malarials. TMPK (thymidylate kinase) is a good candidate as it is essential for the synthesis of dTTP, a critical precursor of DNA and has been much studied due to its role in prodrug activation and as a drug target. Type I TMPKs, such as the human enzyme, phosphorylate the substrate AZT (3'-azido3'-deoxythymidine)-MP (monophosphate) inefficiently compared with type II TMPKs (e.g. Escherichia coli TMPK). In the present paper we report that eukaryotic PfTMPK (P falciparum TMPK) presents sequence features of a type I enzyme yet the kinetic parameters for AZT-MP phosphorylation are similar to those of the highly efficient E. coli enzyme. Structural information shows that this is explained by a different juxtaposition of the P-loop and the azide of AZT-MP. Subsequent formation of the transition state requires no further movement of the PfTMPK P-loop, with no steric conflicts for the azide moiety, allowing efficient phosphate transfer. Likewise, we present results that confirm the ability of the enzyme to uniquely accept dGMP as a substrate and shed light on the basis for its wider substrate specificity. Information resulting from two ternary complexes (dTMP ADP and AZT-MP ADP) and a binary complex with the transition state analogue AP(5)dT [P-1-(5'-adenosyl)-P-5-(5'-thymidyl) pentaphosphate] all reveal significant differences with the human enzyme, notably in the lid region and in the P-loop which may be exploited in the rational design of Plasmodium-specific TMPK inhibitors with therapeutic potential.

Original languageEnglish
Pages (from-to)499-509
Number of pages11
JournalBiochemical journal
Issue number3
Publication statusPublished - 15 Jun 2010


  • drug target
  • ligand complex
  • malaria
  • Plasmodium falciparum
  • thymidylate kinase (TMPK)

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