Yamamoto Y, Iwafune K, Chûjô R, Inoue Y, Imai K, Suzuki T
Department of Biomolecular Engineering, Tokyo Institute of Technology.
J Biochem. 1992 Sep;112(3):414-20. doi: 10.1093/oxfordjournals.jbchem.a123914.
1H-NMR spectra of deoxy myoglobins (Mbs) from shark (Galeorhinus japonicus), horse, and sperm whale have been studied to gain insights into their active site structure. It has been demonstrated for the first time that nuclear Overhauser effect (NOE) can be observed between heme peripheral side-chain proton resonances of these paramagnetic complexes. Val-E11 methyl and His-F8 C delta H proton resonances of these Mbs were also assigned from the characteristic shift and line width. The hyperfine shift of the former resonance was used to calculate the magnetic anisotropy of the protein. The shift analysis of the latter resonance, together with the previously assigned His-F8 N delta H proton resonance, revealed that the strain on the Fe-N epsilon bond is in the order horse Mb approximately whale Mb < shark Mb and that the hydrogen bond strength of the His-F8 N delta H proton to the main-chain carbonyl oxygen in the preceding turn of the F helix is in the order shark Mb < horse Mb < whale Mb. Weaker Feporphyrin interaction in shark Mb was manifested in a smaller shift of the heme methyl proton resonance and appears to result from distortion of the coordination geometry in this Mb. Larger strain on the Fe-N epsilon bond in shark Mb should be to some extent attributed to its lowered O2 affinity (P50 = 1.1 mmHg at 20 degrees C), compared to whale and horse Mbs.
对来自鲨鱼（日本真鲨）、马和抹香鲸的脱氧肌红蛋白（Mb）的1H-NMR光谱进行了研究，以深入了解它们的活性位点结构。首次证明，在这些顺磁性复合物的血红素外周侧链质子共振之间可以观察到核Overhauser效应（NOE）。这些Mb的Val-E11甲基和His-F8 CδH质子共振也根据特征性位移和线宽进行了归属。利用前者共振的超精细位移来计算蛋白质的磁各向异性。对后者共振的位移分析，连同先前归属的His-F8 NδH质子共振，表明Fe-Nε键上的应变顺序为马肌红蛋白≈鲸肌红蛋白＜鲨鱼肌红蛋白，并且His-F8 NδH质子与F螺旋前一圈主链羰基氧之间的氢键强度顺序为鲨鱼肌红蛋白＜马肌红蛋白＜鲸肌红蛋白。鲨鱼肌红蛋白中较弱的铁卟啉相互作用表现为血红素甲基质子共振的较小位移，这似乎是由于该肌红蛋白中配位几何结构的扭曲所致。与鲸和马的肌红蛋白相比，鲨鱼肌红蛋白中Fe-Nε键上较大的应变在一定程度上应归因于其较低的O2亲和力（20℃时P50 = 1.1 mmHg）。
