Weichsel A, Andersen J F, Roberts S A, Montfort W R
Department of Biochemistry, University of Arizona, Tucson, Arizona 85721, USA.
Nat Struct Biol. 2000 Jul;7(7):551-4. doi: 10.1038/76769.
The nitrophorins comprise an unusual family of proteins that use ferric (Fe(III)) heme to transport highly reactive nitric oxide (NO) from the salivary gland of a blood sucking bug to the victim, resulting in vasodilation and reduced blood coagulation. We have determined structures of nitrophorin 4 in complexes with H2O, cyanide and nitric oxide. These structures reveal a remarkable feature: the nitrophorins have a broadly open distal pocket in the absence of NO, but upon NO binding, three or more water molecules are expelled and two loops fold into the distal pocket, resulting in the packing of hydrophobic groups around the NO molecule and increased distortion of the heme. In this way, the protein apparently forms a 'hydrophobic trap' for the NO molecule. The structures are very accurate, ranging between 1.6 and 1.4 A resolutions.
亲铁蛋白是一类独特的蛋白质家族，它们利用三价铁（Fe(III)）血红素将高活性一氧化氮（NO）从吸血昆虫的唾液腺运输到受害者体内，从而导致血管舒张和血液凝固减缓。我们已经确定了亲铁蛋白4与水、氰化物和一氧化氮形成的复合物的结构。这些结构揭示了一个显著特征：在没有NO的情况下，亲铁蛋白具有一个广泛开放的远端口袋，但在NO结合后，三个或更多水分子被排出，两个环折叠进入远端口袋，导致疏水性基团围绕NO分子堆积，并增加了血红素的扭曲。通过这种方式，蛋白质显然为NO分子形成了一个“疏水陷阱”。这些结构非常精确，分辨率在1.6至1.4埃之间。
