STRUCTURE OF CYTOPLASMIC REGION OF LEUKOCYTE ANTIGEN RELATED (LAR) PROTEIN

与细胞色素P450 cam络合的晶体结构 (S)尼古丁的测定值为2.3决议。(S)-尼古丁 已被广泛研究为细菌P450 cam的底物 和人类P450酶。以前的动力学研究已经检验了 (S)-尼古丁与P450cam的结合(Jones等人，1993年，J.Am化学。 SoC。115、381-387。)。这些都表明(S)-尼古丁经历了 吡咯烷5‘碳上的区域特异性单氧基，暗示 分子定位于具有吡咯环的活性中心 接近催化的血红素铁。相比之下，晶体结构 显示尼古丁分子的方向与 吡啶氮与亚铁血红素配位。这一点是一致的 通过紫外光谱研究，表明形成了一个低自旋 六配位铁对溶液中尼古丁与P450钙调素结合的影响 (同上)。然而，吡咯烷5‘碳大约为8从… 晶体结构中的血红素铁，表明这是 代表了一种非生产性的，尽管在能量上有利的约束性 模式。这些发现将在第17届国际 生物学和分子生物学大会，1997年8月，旧金山， 并正在撰写出版(见下文)。其他内容 目前的研究正在研究配体可能的重新定向 有效的捆绑。其中包括(S)-尼古丁结合的检查 在CO存在的还原条件下还原为P450cam。

The crystal structure of cytochrome P450cam complexed with (S)-nicotine has been determined at 2.3
resolution. (S)-nicotine has been extensively studied as a substrate of both bacterial P450cam and human P450 enzymes. Previous kinetic studies have examined (S)-nicotine binding to P450cam (Jones et al., 1993, J. Am. Chem. Soc. 115, 381-387.). These demonstrate that (S)-nicotine undergoes regiospecific monooxygenation at the pyrrolidine 5' carbon, implying that the molecule orients in the active site with the pyrrolidine ring close to the catalytic heme iron. In contrast, the crystal structure shows the nicotine molecule in a reversed orientation with the pyridine nitrogen coordinated with the heme iron. The is consistent with UV spectral studies, which indicate formation of a low-spin hexacoordinate iron upon nicotine binding to P450cam in solution (Ibid.). However, the pyrrolidine 5' carbon is approximately 8
from the heme iron in the crystal structure, indicating that this represents a nonproductive, though energetically favorable, binding mode. These findings will be presented at the 17th International Congress of Biology and Molecular Biology, August 1997, San FRancisco, and are being written up for publication (see below). Additional studies are now examining possible reorientation of the ligand for productive binding. These include examination of (S)-nicotine binding to P450cam in the presence of CO under reducing conditions.