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首页> 外文期刊>Journal of biological inorganic chemistry: JBIC: a publication of the Society of Biological Inorganic Chemistry >Assignment of the ferriheme resonances of high- and low-spin forms of the symmetrical hemin-reconstituted nitrophorins 1-4 by H-1 and C-13 NMR spectroscopy: the dynamics of heme ruffling deformations
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Assignment of the ferriheme resonances of high- and low-spin forms of the symmetrical hemin-reconstituted nitrophorins 1-4 by H-1 and C-13 NMR spectroscopy: the dynamics of heme ruffling deformations

机译：通过H-1和C-13 NMR光谱确定高和低旋形式的对称的血红素重构的硝酸盐蛋白1-4的亚铁血红素共振：血红素波纹的动力学

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摘要

The four major nitrophorins (NPs) of the adult blood-sucking insect Rhodnius prolixus have been reconstituted with the "symmetrical hemin" 2,4-dimethyldeuterohemin, and their NMR spectra have been investigated as the high-spin (S = 5/2) aqua and low-spin (S = 1/2) N-methylimidazole (NMeIm) and cyanide complexes. The NMeIm complexes allow assignment of the high-spin hemin resonances by saturation transfer difference spectroscopy. The cyanide complexes were investigated as paramagnetic analogues of the NO complexes. It is shown that the hemin ring is highly distorted from planarity, much more so for NP2 than for NP1 and NP4 (with ruffling being the major distortion mode), for both high- and low-spin forms. For the cyanide complexes, the conformation of the distorted ring changes on the NMR timescale to yield chemical exchange (exchange spectroscopy, EXSY) cross peaks for NP1sym(CN), NP3sym(CN) and NP4sym(CN) but not for NP2sym(CN). These changes in nonplanar conformation are visualized as a "rolling" of the ruffled macrocycle ridges through some number of degrees, the lowest-energy ruffling mode. This probably occurs in response to slow protein dynamics that cause the I120 and L132 side chains in the distal heme pocket to move in opposite directions (up and away vs. down and toward the hemin ring). This in turn changes the out-of-plane displacements of the 2M and 3M of the symmetrical hemin on the NMR timescale. Two other types of dynamics, i.e., changes in heme seating and NMeIm rotation, are also observed. The highly distorted heme and the dynamics it causes are unique to the NPs and a few other heme proteins with highly distorted macrocycles.
机译：成年吸血昆虫Rhodnius prolixus的四种主要硝化蛋白（NPs）已用“对称性血红素” 2,4-二甲基氘血红素重构，并且其NMR光谱已作为高自旋性进行了研究（S = 5/2）水和低旋转（S = 1/2）N-甲基咪唑（NMeIm）和氰化物配合物。 NMeIm复合物可通过饱和转移差光谱法分配高自旋血红素共振。研究了氰化物配合物作为NO配合物的顺磁性类似物。结果表明，对于高自旋形式和低自旋形式，血红素环的平面度高度失真，与NP1和NP4相比，NP2的失真要大得多（以波纹为主要失真模式）。对于氰化物络合物，扭曲的环的构型在NMR时标上发生变化，从而产生NP1sym（CN），NP3sym（CN）和NP4sym（CN）的化学交换（交换光谱，EXSY）交叉峰。非平面构型的这些变化可视为皱纹的大环隆起“滚动”了一定程度，即最低能量的波动模式。这可能是由于缓慢的蛋白质动力学而引起的，该动力学导致远端血红素袋中的I120和L132侧链沿相反方向移动（上下移动与向下移动并向血红素环移动）。反过来，这会在NMR时标上改变对称血红素的2M和3M的平面外位移。还观察到另外两种类型的动力学，即血红素就座和NMeIm旋转的变化。高度变形的血红素及其引起的动力学是NP和其他一些具有高度变形的大环的血红素蛋白所独有的。

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