Biophysical Society Thematic Meeting - November 16-20, 2015

Biophysics in the Understanding, Diagnosis, and Treatment of Infectious Diseases Speaker Abstracts

Structure-inspired Disruption of Proper Folding of an Essential Malaria Parasite Protein Bennett Z. Guo, Devaraja G. Mudeppa, Pradipsinh Rathod . University of Washington, Seattle, USA. Successful drug design involves potent and selective binding of small molecules to active-sites of drugable targets such as Plasmodium falciparum dihydrofolate reductase-thymidylate synthase ( Pf DHFR-TS). In addition to identification of new drug targets, such as P. falciparum dihydroorotate dehydrogenase ( Pf DHODH), it would be helpful to identify new ways to selectively attack existing high-value parasite protein targets. Many protozoans, including malaria parasites, code for more than one enzyme on the same multifunctional protein, while host cells have separate corresponding enzymes. Here, we examine whether proper folding and catalytic activity of the trailing thymidylate synthase ( Pf TS) domain relies on the leading enzyme, dihydrofolate reductase ( Pf DHFR). Guided by the protein structure of the bifunctional enzyme and cell-free protein expression of individual domains, truncated Pf TS mRNA was translated either by itself, with Pf DHFR mRNA, or with purified Pf DHFR protein. Activity assays showed that Pf DHFR protein was required as a template for functional folding of the Pf TS domain. Structural interactions between the folded Pf DHFR and nucleation sites for proper initiation of Pf TS folding were identified by a combination of structure biology, “non-active site” mutations on Pf DHFR, and identification of inhibitory synthetic peptides based on predicted critical inter-doman contact residues. These insights open exciting new ways to target species-specific protein-protein interactions in malaria parasites and possibly other pathogens.

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