Structural studies on Enterococcus faecalis HMG-CoA reductase: A target for structure based drug design

Sucharita Bose, Purdue University

Abstract

Enterococcus faecalis is a gram-positive bacterium causing bacteremia, urinary tract infections and infective endocarditis. Acquisition of resistance to several antibiotics has led to emergence of E. faecalis as a nosocomial pathogen posing a considerable therapeutic challenge. E. faecalis, along with other gram-positive cocci, rely on the mevalonate pathway for isoprenoid biosynthesis critical for their survival. Thus, the enzymes of the mevalonate pathway are considered as potential candidates for drug targets. In E. faecalis, HMG-CoA reductase catalyzes the NADPH-dependent reduction of HMG-CoA to mevalonate. Bacterial HMG-CoA reductase and its eukaryotic counterpart differ in regulation and sensitivity toward statins, which reflects an underlying structural difference that can be exploited to generate specific antibiotics targeted against E. faecalis. The structure of the E.faecalis enzyme has been solved at 2.25 Å by the molecular replacement method using the bacterial P. mevalonii enzyme as the search model. The crystal structure of E. faecalis HMG-CoA reductase in complex with HMG-CoA and NADP + has also been solved. As for the other HMG-CoA reductases, this structure shows a dimer as the functional catalytic unit. Each monomer comprises a large domain that binds HMG-CoA and a small NADP+ binding domain. The structure shows a close resemblance to the P. mevalonii enzyme in its active site while possessing new structural features determining its specificity towards NADP+ over NAD+ . Potential inhibitors have been identified from a high throughput screen and subsequent structural analysis with the enzyme reveals their mode of inhibition. The lead compounds are currently undergoing refinement in order to produce a "drug-like" compound.

Degree

Ph.D.

Advisors

Bose, Purdue University.

Subject Area

Pharmaceutical sciences|Biophysics

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