Miller Bradley R, Kung Yan
Department of Chemistry, Bryn Mawr College , 101 North Merion Avenue, Bryn Mawr, Pennsylvania 19010, United States.
Biochemistry. 2018 Feb 6;57(5):654-662. doi: 10.1021/acs.biochem.7b00999. Epub 2017 Dec 21.
The key mevalonate pathway enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (HMGR) uses the cofactor NAD(P)H to reduce HMG-CoA to mevalonate in the production of countless metabolites and natural products. Although inhibition of HMGR by statin drugs is well-understood, several mechanistic details of HMGR catalysis remain unresolved, and the structural basis for the wide range of cofactor specificity for either NADH or NADPH among HMGRs from different organisms is also unknown. Here, we present crystal structures of HMGR from Streptococcus pneumoniae (SpHMGR) alongside kinetic data of the enzyme's cofactor preferences. Our structure of SpHMGR bound with its kinetically preferred NADPH cofactor suggests how NADPH-specific binding and recognition are achieved. In addition, our structure of HMG-CoA-bound SpHMGR reveals large, previously unknown conformational domain movements that may control HMGR substrate binding and enable cofactor exchange without intermediate release during the catalytic cycle. Taken together, this work provides critical new insights into both the HMGR reaction mechanism and the structural basis of cofactor specificity.
关键的甲羟戊酸途径酶3-羟基-3-甲基戊二酰辅酶A（HMG-CoA）还原酶（HMGR）利用辅因子NAD(P)H将HMG-CoA还原为甲羟戊酸，用于生产无数的代谢产物和天然产物。尽管他汀类药物对HMGR的抑制作用已被充分了解，但HMGR催化的一些机制细节仍未解决，不同生物体的HMGR对NADH或NADPH具有广泛辅因子特异性的结构基础也尚不清楚。在此，我们展示了肺炎链球菌HMGR（SpHMGR）的晶体结构以及该酶辅因子偏好的动力学数据。我们的SpHMGR与其动力学偏好的NADPH辅因子结合的结构表明了NADPH特异性结合和识别是如何实现的。此外，我们的结合HMG-CoA的SpHMGR结构揭示了以前未知的大的构象结构域运动，这些运动可能控制HMGR底物结合，并在催化循环中实现辅因子交换而无需中间产物释放。综上所述，这项工作为HMGR反应机制和辅因子特异性的结构基础提供了重要的新见解。
