CRYSTALLOGRAPHIC STUDIES ON NITRIC OXIDE SYNTHASES

内皮细胞一氧化氮合酶血红素结构域的晶体结构 一氧化氮合酶（eNOS）已被确定为1.9
. NOS是酶 将L-精氨酸转化为一氧化氮（NO）和L-瓜氨酸。 NO是 免疫，心血管， 和神经系统。 NO过量生产和生产不足都与 与一些病理条件，所以同种型的设计 特异性抑制剂是重要的健康相关目标。 NOS必须是 二聚体的功能，因为血红素结构域是关键的目标 对于药物设计，我们关注血红素结构域的结构 二聚体。 结构为1.9
含有一种有效的抑制剂， 乙基异硫脲，结合在活性位点和2.3
得双曲余切值. 确定了基质复合物的结构。 使用 同步辐射源对这项工作是绝对必要的。 晶体内部折射率约为3.0-3.5
但超过1.9
在 同步辐射源 此外，大量使用异常 分散信息对于获得可解释的 电子密度图 一个意想不到的和新颖的功能， 结构是由成对的金属配位的识别， 沿二联体沿着二聚体界面处的对称性相关Cys残基 对称轴 由于几个数据集是在不同的 在国际象棋和其他来源的波长，有可能使用 异常差异傅立叶谱来识别金属为锌。 的 金属对于形成必需的结合位点至关重要， 辅因子，四氢生物蝶呤，这反过来，是重要的形成 底物结合位点。 新金属S_4的鉴定 集群为NOS结构提供了重要的新见解， 如果没有同步加速器X射线， 源

The crystal structure of the heme domain of endothelial nitric oxide synthase (eNOS) has been determined to 1.9
. NOS is the enzyme that converts L-arginine to nitric axide (NO) and L-citrulline. NO is a ptent biological signaling molecule in the immune, cardiovascular, and nervous systems. Both NO over and under production are associated with a number of pathological conditions so the design of isoform specific inhibitors is an important health related goal. NOS must be dimeric to function and since the heme domain is the critical target for drug design, we have focused on the structure of heme domain dimers. The structure to 1.9
contains a potent inhibitor, ehtylisothiourea, bound at the active site and at 2.3
, the substrate-complex structure has been determined. The use of synchrotron radiation sources was absolutely essential for this work. Crystals diffract inhouse to about 3.0-3.5
but beyond 1.9
at synchrotron sources. In addition, extensive use of anomalous dispersion information was essential for obtaining an interpretable electron density map. An unexpected and novel feature in the structure is the identification of metal coordinated by pairs of symmetry related Cys residues at the dimer interface along the dyad axis of symmetry. Since several data sets were obtained at various wavelengths at CHESS and at other sources, it was possible to use anomalous difference Fouriers to identify the metal as zinc. The metal is crucial for forming the binding site for the essential cofactor, tetrhydrobiopterin, which in turn, is important for forming the substrate binding site. The identification of the new metal-S4 cluster has provided significant new insights into NOS structure and function which would not have been possible without synchrotron x-ray sources.