Ligand-induced heme ruffling and bent no geometry in ultra-high-resolution structures of nitrophorin 4.
Ligand-induced heme ruffling and bent no geometry in ultra-high-resolution structures of nitrophorin 4.
复制标题
硝基蛋白 4 的超高分辨率结构中配体诱导的血红素褶皱和弯曲无几何形状。
DOI：
10.1021/bi0109257
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发表时间：
2001
期刊：
影响因子：
2.9
通讯作者：
Montfort,WR
中科院分区：
文献类型：
--
作者：
Roberts,SA;Weichsel,A;Qiu,Y;Shelnutt,JA;Walker,FA;Montfort,WR
硝化蛋白是一个蛋白质家族，利用铁血红素将一氧化氮（NO）从吸血昆虫的唾液腺运输到受害者，导致血管舒张和血液凝固减少。我们对Rhodnius prolixus中的nitrophorin 4（NP 4）与NO（1.08 μ mol）和NH3（1.15 μ mol）络合物的原子分辨率结构进行了改进，得到了铁配位层的高度详细的图像。在NP4 − NO中，NO氮与铁配位（Fe-N距离= 1.66 °），并有些弯曲（Fe-N − O角= 156 °），弯曲发生在与近端组氨酸环相同的平面上。Fe（NO）（血红素）（His）的配位几何形状是不寻常的，但与Fe（III）的氧化态是一致的，这是稳定的高度皱褶血红素。血红素皱褶发生在两种结构中，显然是由于血红素和亮氨酸123和133之间的密切接触，但增加结合NO，即使空间接触没有改变。我们还报告了与组胺（1.50 μ l）和咪唑（1.27 μ l）复合的NP 4的结构。出乎意料的是，两个移动的环在NP 4 − NO中重新排列以与结合的NO相结合，也在NP 4 −咪唑复合物中重新排列。这种构象变化显然是由NO和咪唑（结合）配体的非极性性质驱动的。总之，通过蛋白质构象的变化，NO结合口袋的去溶剂化，以及NO部分的弯曲，可能通过蛋白质辅助的血红素皱褶，可能导致亚硝酰-血红素复合物异常地抵抗自还原。
The nitrophorins are a family of proteins that use ferric heme to transport nitric oxide (NO) from the salivary glands of blood-sucking insects to their victims, resulting in vasodilation and reduced blood coagulation. We have refined atomic resolution structures of nitrophorin 4 (NP4) fromRhodnius prolixuscomplexed with NO (1.08 Å) and NH3(1.15 Å), yielding a highly detailed picture of the iron coordination sphere. In NP4−NO, the NO nitrogen is coordinated to iron (Fe−N distance = 1.66 Å) and is somewhat bent (Fe−N−O angle = 156°), with bending occurring in the same plane as the proximal histidine ring. The Fe(NO)(heme)(His) coordination geometry is unusual but consistent with an Fe(III) oxidation state that is stabilized by a highly ruffled heme. Heme ruffling occurs in both structures, apparently due to close contacts between the heme and leucines 123 and 133, but increases on binding NO even though the steric contacts have not changed. We also report the structure of NP4 in complexes with histamine (1.50 Å) and imidazole (1.27 Å). Unexpectedly, two mobile loops that rearrange to pack against the bound NO in NP4−NO, also rearrange in the NP4−imidazole complex. This conformational change is apparently driven by the nonpolar nature of the NO and imidazole (as bound) ligands. Taken together, the desolvation of the NO binding pocket through a change in protein conformation, and the bending of the NO moiety, possibly through protein-assisted heme ruffling, may lead to a nitrosyl−heme complex that is unusually resistant to autoreduction.