Solution 1H-NMR structure of the heme cavity in the low-affinity state for the allosteric monomeric cyano-met hemoglobins from Chironomus thummi thummi. Comparison to the crystal structure.
Solution 1H-NMR structure of the heme cavity in the low-affinity state for the allosteric monomeric cyano-met hemoglobins from Chironomus thummi thummi. Comparison to the crystal structure.
复制标题
来自摇蚊的变构单体氰基-met 血红蛋白处于低亲和力状态的血红素腔的溶液 1H-NMR 结构。
DOI：
10.1111/j.1432-1033.1996.0841p.x
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Gersonde,K
中科院分区：
文献类型：
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作者：
Zhang,W;LaMar,GN;Gersonde,K
对来自昆虫Chironomus thummi thummi的单体血红蛋白III和IV的氰基复合物进行了血红素腔的溶液1H-NMR研究，其中每一种都表现出明显的玻尔效应。选择低pH 5的顺磁性（S= 1/2）衍生物进行研究，因为大的偶极位移提供了相对于抗磁性形式的改进的分辨率，并且允许区分两种异构血红素取向[佩顿，D. H、拉马尔湾N. & Gersonde，K.（1988）Biochim. Biophys. Acta 954，82-94]。此外，已经报道了血红蛋白III衍生物的低pH形式的晶体结构，并显示功能上涉及的远端His 58侧链采用替代取向，在口袋内或口袋外[Steigemann，W.和韦伯，E。等（1979）J. Mol. 127，309-338]。基于核Overhauser对血红素和彼此的效应、偶极位移和顺磁诱导弛豫，两种血红蛋白的低pH形式的所有血红素口袋残基至少部分位于血红素腔中。由此产生的结构产生的顺磁磁化率张量的主轴方向。的氰血红蛋白III和IV的血红素口袋结构被发现是难以区分的，都表现出远端His 58取向的唯一进入血红素腔和接触的配体，并与两个残基，Phe 100和Phe 38，表现出小，但显着的位移在溶液中相对于血红蛋白III在晶体中。
Solution1H‐NMR studies of the heme cavity were performed for the cyanomet complexes of monomeric hemoglobins III and IV from the insectChironomus thummi thummi, each of which exhibit marked Bohr effects. The low pH 5, paramagnetic (S= 1/2) derivatives were selected for study because the large dipolar shifts provide improved resolution over diamagnetic forms and allow distinction between the two isomeric heme orientations [Peyton, D. H., La Mar, G. N. & Gersonde, K. (1988)Biochim. Biophys. Acta954, 82–94]. The crystal structure for the low‐pH form of the hemoglobin III derivative, moreover, has been reported and showed that the functionally implicated distal His58 side chain adopts alternative orientations, either in or out of the pocket [Steigemann, W. & Weber, E. (1979)J. Mol. Biol. 127, 309–338]. All heme pocket residues for the low‐pH forms of the two hemoglobins were located, at least in part, and positioned in the heme cavity on the basis of nuclear Overhauser effects to the heme and each other, dipolar shifts, and paramagnetic‐induced relaxation. The resulting structure yielded the orientation of the major axis of the paramagnetic susceptibility tensor. The heme pocket structure of the cyanomet hemoglobins III and IV were found to be indistinguishable, with both exhibiting a distal His58 oriented solely into the heme cavity and in contact with the ligand, and with two residues, Phe100 and Phe38, exhibiting small but significant displacements in solution relative to hemoglobin III in the crystal.