Hauptman-Woodward Medical Research Institute, The State University of New York at Buffalo, 700 Ellicott Street, Buffalo, NY 14203, USA.
J Struct Biol. 2011 Nov;176(2):254-8. doi: 10.1016/j.jsb.2011.07.019. Epub 2011 Aug 6.
The cyclooxygenases (COX-1 and COX-2) are membrane-associated, heme-containing homodimers that generate prostaglandin H(2) from arachidonic acid (AA) in the committed step of prostaglandin biogenesis and are the targets for nonsteroidal anti-inflammatory drugs (NSAIDs). N-(2-cyclohexyloxy-4-nitrophenyl) methanesulfonamide (NS-398) was the first in a series of isoform-selective drugs designed to preferentially inhibit COX-2, with the aim of ameliorating many of the toxic gastrointestinal side effects caused by conventional NSAID inhibition. We determined the X-ray crystal structure of murine COX-2 in complex with NS-398 utilizing synchrotron radiation to 3.0A resolution. NS-398 binds in the cyclooxygenase channel in a conformation that is different than that observed for other COX-2-selective inhibitors, such as celecoxib, with no discernible penetration into the side pocket formed in COX-2 by the isoform-specific substitutions of I434V, H513R, and I523V. Instead, the methanesulfonamide moiety of NS-398 interacts with the side chain of Arg-120 at the opening of the cyclooxygenase channel, similar to that observed for acidic, nonselective NSAIDs such as indomethacin and flurbiprofen. Our structure validates inhibitor studies that identified Arg-120 as a molecular determinant for time-dependent inhibition of COX-2 by NS-398.
环氧化酶（COX-1 和 COX-2）是膜相关的、含有血红素的同源二聚体，它在前列腺素生物合成的关键步骤中，从花生四烯酸（AA）生成前列腺素 H2，是非甾体抗炎药（NSAIDs）的作用靶点。N-（2-环己氧基-4-硝基苯基）甲磺酰胺（NS-398）是一系列同工酶选择性药物中的第一个，旨在优先抑制 COX-2，目的是改善传统 NSAID 抑制引起的许多胃肠道毒性副作用。我们利用同步辐射技术将鼠 COX-2 与 NS-398 复合物的 X 射线晶体结构解析至 3.0A 分辨率。NS-398 结合在环氧化酶通道中，构象与其他 COX-2 选择性抑制剂（如塞来昔布）观察到的不同，没有明显进入 COX-2 由同工酶特异性取代 I434V、H513R 和 I523V 形成的侧袋。相反，NS-398 的甲磺酰胺部分与环氧化酶通道开口处的 Arg-120 侧链相互作用，类似于酸性、非选择性 NSAIDs（如吲哚美辛和氟比洛芬）的情况。我们的结构验证了抑制剂研究，这些研究确定 Arg-120 是 NS-398 对 COX-2 的时间依赖性抑制的分子决定因素。
