Structural studies of constitutive nitric oxide synthases with diatomic ligands bound
Structural studies of constitutive nitric oxide synthases with diatomic ligands bound
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DOI：
10.1007/s00775-006-0123-8
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发表时间：
2006-09-01
影响因子：
3
通讯作者：
Poulos, Thomas L.
中科院分区：
文献类型：
--
作者：
Li, Huiying;Igarashi, Jotaro;Poulos, Thomas L.
晶体结构的内皮型一氧化氮合酶（eNOS）-精氨酸-CO三元复合物以及神经元型一氧化氮合酶（nNOS）血红素结构域与L-精氨酸和双原子配体，CO或NO，在天然的辅因子，四氢生物蝶呤，或其氧化类似物，二氢生物蝶呤和4-氨基生物蝶呤的存在下复合。生物蝶呤的性质对双原子配体结合没有影响。双原子配体与一氧化氮合酶（NOS）的结合几何构型遵循从无机金属配合物发展而来的{MXY}（n）形式。结构揭示了eNOS和nNOS之间的一些微妙的结构差异时，CO绑定到血红素，以及相关的CO伸缩频率的差异，通过共振拉曼技术。在nNOS结构的活性位点中描绘的详细氢键合几何形状表明，有序的活性位点水分子而不是底物本身最有可能充当与血红素结合的双原子配体（CO、NO以及O2）的直接质子供体。这对NOS催化的氧活化机制至关重要。
Crystal structures are reported for the endothelial nitric oxide synthase (eNOS)-arginine-CO ternary complex as well as the neuronal nitric oxide synthase (nNOS) heme domain complexed with L-arginine and diatomic ligands, CO or NO, in the presence of the native cofactor, tetrahydrobiopterin, or its oxidized analogs, dihydrobiopterin and 4-aminobi-opterin. The nature of the biopterin has no influence on the diatomic ligand binding. The binding geometries of diatomic ligands to nitric oxide synthase (NOS) follow the {MXY}(n) formalism developed from the inorganic diatomic-metal complexes. The structures reveal some subtle structural differences between eNOS and nNOS when CO is bound to the heme which correlate well with the differences in CO stretching frequencies observed by resonance Raman techniques. The detailed hydrogen-bonding geometries depicted in the active site of nNOS structures indicate that it is the ordered active-site water molecule rather than the substrate itself that would most likely serve as a direct proton donor to the diatomic ligands (CO, NO, as well as 02) bound to the heme. This has important implications for the oxygen activation mechanism critical to NOS catalysis.