Kaminaka S, Takizawa H, Handa T, Kihara H, Kitagawa T
Institute for Molecular Science, Okazaki National Research Institutes, Japan.
Biochemistry. 1992 Aug 4;31(30):6997-7002. doi: 10.1021/bi00145a018.
Resonance Raman spectra were observed for the oxy and azidomet forms of a cooperative hemerythrin (Hr) isolated from Lingula unguis and a noncooperative Hr from Siphonosoma cumanense. The O-O stretching frequency of the oxy derivative of the L. unguis Hr was lower in the high-affinity form generated at pH 7.6 than in the low-affinity form generated at pH 6.2, while that of the S. cumanense Hr did not change at those two pH values. The Fe-O-Fe symmetric stretching mode of L. unguis azidomet-Hr exhibited a frequency shift between pH 7.6 and 6.2, while that of S. cumanense was not shifted. However, the corresponding band of the oxy form did not show a pH-dependent frequency change. Therefore, it is noted that the azidomet form is not a suitable model for studying a mechanism of cooperativity, contrary to the structural similarity between the oxy and azidomet forms. The Fe-O2 as well as Fe-N3 stretching frequencies were found to have no relation with the oxygen affinity. Upon exchange of solvent from H2O to D2O, the O-O and Fe-O2 stretching modes of L. unguis Hr were shifted to higher and lower frequencies, respectively, and their magnitudes were the same for the high- and low-affinity forms. The same frequency shifts were observed for S. cumanense Hr.(ABSTRACT TRUNCATED AT 250 WORDS)
对从中华舌形贝分离得到的协同型蚯蚓血红蛋白（Hr）的氧合形式和叠氮甲酰形式以及来自库曼海豆芽的非协同型Hr进行了共振拉曼光谱观测。中华舌形贝Hr的氧合衍生物的O - O伸缩频率在pH 7.6时产生的高亲和力形式中比在pH 6.2时产生的低亲和力形式中更低，而库曼海豆芽Hr的该频率在这两个pH值下没有变化。中华舌形贝叠氮甲酰 - Hr的Fe - O - Fe对称伸缩模式在pH 7.6和6.2之间表现出频率偏移，而库曼海豆芽的该模式没有偏移。然而，氧合形式的相应谱带未显示出pH依赖性频率变化。因此，需要注意的是，与氧合形式和叠氮甲酰形式之间的结构相似性相反，叠氮甲酰形式并非研究协同作用机制的合适模型。发现Fe - O₂以及Fe - N₃伸缩频率与氧亲和力无关。当溶剂从H₂O交换为D₂O时，中华舌形贝Hr的O - O和Fe - O₂伸缩模式分别向更高和更低频率移动，并且它们在高亲和力和低亲和力形式中的移动幅度相同。库曼海豆芽Hr也观察到相同的频率移动。（摘要截断于250字）
