Biophysical Society Thematic Meeting

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 (

DHFR-TS). In addition to identification of new drug targets, such as

falciparum

dihydroorotate dehydrogenase (

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 (

TS)

domain relies on the leading enzyme, dihydrofolate reductase (

DHFR). Guided by the protein

structure of the bifunctional enzyme and cell-free protein expression of individual domains,

truncated

TS mRNA was translated either by itself, with

DHFR mRNA, or with

purified

DHFR protein. Activity assays showed that

DHFR protein was required as a

template for functional folding of the

TS domain. Structural interactions between the

folded

DHFR and nucleation sites for proper initiation of

TS folding were identified by a

combination of structure biology, “non-active site” mutations on

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.