Nuclear-magnetic-resonance investigation of the cooperative homodimeric hemoglobin from the mollusc Scapharca inaequivalvis. Molecular and electronic structure of the cyano-met derivative.
Nuclear-magnetic-resonance investigation of the cooperative homodimeric hemoglobin from the mollusc Scapharca inaequivalvis. Molecular and electronic structure of the cyano-met derivative.
复制标题
来自软体动物 Scapharca inaequivalvis 的协同同二聚血红蛋白的核磁共振研究。
DOI：
10.1111/j.1432-1033.1989.tb14989.x
复制
发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Singh,JP
中科院分区：
文献类型：
--
作者：
McGourty,JL;LaMar,GN;Smith,KM;Ascoli,F;Chiancone,E;Pandey,RK;Singh,JP
研究了来自软体动物scapharca inaequivalals的合作二聚体和四聚体血红蛋白的氰-锰配合物的质子核磁共振波谱，并与其他结构表征的氧结合血红蛋白的质子核磁共振波谱进行了比较。对于这些蛋白质，即使在同型二聚体中也显示出协同性，初步的X射线结构数据显示，亚基间的接触涉及EF螺旋，这是一种不寻常的从后到前的组装[Royer， W. E., Love， W. E. & Fenderson， F. F. (1985)Nature (Lond)]。316年,277 - 280]。超精细位移模式与二聚体和四聚体链非常相似，但与先前表征的低自旋铁血红素蛋白明显不同。个体血红素共振是通过用特殊的氘化血红素重组蛋白质来确定的。虽然涉及近端和远端组氨酸的轴向相互作用与肌红蛋白和其他血红蛋白非常相似，但血红素接触位移模式和氨基酸偶极位移模式都反映了显著减少的不对称性。非配位氨基酸信号传播的减少是根据磁轴相对于肌红蛋白或其他血红蛋白的旋转来解释的，而不是磁各向异性的变化。血红素甲基接触位移的减少支持了这一结论，并且与近端组氨酸的取向相一致，咪唑环相对于其他结构特征蛋白旋转了约30-40°。虽然在蛋白质重组后可以立即检测到与血红素交替取向的复杂模式相关的共振，但分离的蛋白质被发现表现出微不足道的平衡血红素旋转紊乱。
The proton nuclear‐magnetic‐resonance spectra of the cyano‐met complexes of the cooperative dimeric and tetrameric hemoglobins from the molluskScapharca inaequivalvishave been investigated and compared to those of other structurally characterized oxygen binding hemoproteins. For these proteins, cooperativity is displayed even in the homodimer and preliminary X‐ray structural data reveal an unusual back‐to‐front assembly with intersubunit contacts involving the EF helices [Royer, W. E., Love, W. E. & Fenderson, F. F. (1985)Nature (Lond.) 316, 277–280]. The pattern of hyperfine shifts is very similar for the dimer and tetramer chains, but distinctly different from those of previously characterized low‐spin, ferric heme proteins. Individual heme resonances are identified by reconstituting the protein with specifically deuterated hemes. While the axial interactions involving the proximal and distal histidines are very similar to that in myoglobins and other hemoglobins, both the heme contact shift pattern and the amino acid dipolar shift pattern reflect a significantly reduced asymmetry. The decreased spread of the non‐cordinated amino acid signals is interpreted in terms of a rotation of the magnetic axes relative to those in myoglobin or other hemoglobins, rather than a change in the magnetic anisotropy. The decreased spread of the heme methyl contact shifts supports this conclusion and is consistent with an orientation of the proximal histidine with the imidazole ring rotated by about 30–40° relative to that in other structurally characterized proteins. Although resonances associated with a complex pattern of alternate heme orientations can be detected immediately after reconstitution of the protein, the isolated protein was found to exhibit insignificant equilibrium heme rotational disorder.