Nagatomo Shigenori, Jin Yayoi, Nagai Masako, Hori Hiroshi, Kitagawa Teizo
Center for Integrative Bioscience, Okazaki National Research Institutes, Myodaiji, Okazaki, 444-8585, Aichi, Japan.
Biophys Chem. 2002 Jul 10;98(1-2):217-32. doi: 10.1016/s0301-4622(02)00103-5.
Heme-heme interaction in Hb M Boston (His alpha 58-->Tyr) was investigated with visible and UV resonance Raman (RR), EPR, and CD spectroscopies. Although Hb M Boston has been believed to be frozen in the T quaternary state, oxygen binding exhibited appreciable co-operativity (n=1.4) and the near-UV CD spectrum indicated weakening of the T marker at pH 9.0. Binding of CO to the normal beta-subunit gave no change in the EPR and visible Raman spectra of the abnormal alpha-subunit at pH 7.5, but it caused an increase of EPR rhombicity and significant changes in the Raman coordination markers as well as the Fe(III)-tyrosine related bands of the alpha-subunit at pH 9.0. The UVRR spectra indicated appreciable changes of Trp but not of Tyr upon CO binding to the alpha-subunit at pH 9.0. Therefore, we conclude that the ligand binding to the beta heme induces quaternary structure change at pH 9.0 and is communicated to the alpha heme, presumably through His beta 92-->Trp beta 37-->His alpha 87.
采用可见和紫外共振拉曼光谱（RR）、电子顺磁共振（EPR）和圆二色光谱（CD）对血红蛋白M波士顿（Hisα58→Tyr）中的血红素-血红素相互作用进行了研究。尽管一直认为血红蛋白M波士顿处于T四级结构状态，但氧结合表现出明显的协同性（n = 1.4），并且近紫外CD光谱表明在pH 9.0时T标记减弱。在pH 7.5时，CO与正常β亚基的结合并未使异常α亚基的EPR和可见拉曼光谱发生变化，但在pH 9.0时，它导致了EPR菱形度增加以及拉曼配位标记以及α亚基的Fe(III)-酪氨酸相关谱带发生显著变化。紫外共振拉曼光谱表明，在pH 9.0时，CO与α亚基结合后，色氨酸有明显变化，而酪氨酸没有。因此，我们得出结论，在pH 9.0时，配体与β血红素的结合会诱导四级结构变化，并可能通过Hisβ92→Trpβ37→Hisα87传递给α血红素。
