Time-Resolved Crystallography Measurements Elucidating the Mechanism of Bacterial HMG-CoA Reductase

HMG-CoA reductase (HMGR) is the rate limiting enzyme in the Mevalonate pathway that converts 3-hydroxy-3-methylglutarylCoA (HMG-CoA), an intermediate in the metabolic pathway, into Mevalonate which is a precursor compound used in the formation of steroids and cholesterol. Hence, it is the target of cholesterol-lowering drugs, commonly known as statins, that are used to treat patients suffering from hypercholesterolemia. Since the mevalonate pathway is also critical for the survival of multiple gram-positive bacteria, HMG-CoA reductase can also act as a target for novel antibacterials. The mechanism of the bacterial enzyme in Pseudomonas mevalonii has previously been studied and characterized by Steussy et. al (2013) and Haines et. al (2012) resulting in the hypothesis that the substrate, HMG-CoA undergoes conversion into two intermediates, Mevaldyl-CoA and Mevaldehyde, before it is converted into the product, Mevalonate. However, the presence of only one of the intermediates, Mevaldyl-CoA, has been structurally observed by Steussy et. al (2013). Understanding the structural changes that the bacterial enzyme undergoes at the catalytic site during the conversion of substrate to product can help us better understand its mechanism in order to design inhibitors for HMGR. Current work on HMGR focuses on identifying conditions that are suitable for running the enzymatic reaction in the crystal and also altering the rate of the reaction within the HMGR crystal to trap and observe the intermediates formed during catalysis.