Heme-Heme Oxygenase Complex: Structure and Properties of the Catalytic Site from Resonance Raman Scattering

Satoshi Takahashi, Jianling Wang, Denis L. Rousseau, Kazunobu Ishikawa, Tadashi Yoshida, Noriko Takeuchi, Masao Ikeda-Saito

研究成果: Article査読

94 被引用数 (Scopus)


The resonance Raman spectra of ferric and ferrous forms of the heme-heme oxygenase (HO) complex (isoform 1) clarify several structural features of the catalytic active site. Isotopic substitution studies of the central iron atom of the heme demonstrate that the line at 218 cm−1 in the ferrous ligand-free form of the complex originates from the iron-histidine stretching mode. The presence of a Raman line at this frequency confirms that the fifth ligand coordinating to the heme is a neutral imidazole from a histidine residue. The modes associated with CO in the carboxy derivative of the ferrous enzyme complex have typical frequencies of histidine-bound heme proteins such as myoglobin. In the ferric form of the complex, at alkaline pH, hydroxide is identified as the bound exogenous ligand, and at neutral pH we infer that water is bound. Thus, the coordination of the heme-HO complex is the same as that in myoglobin. However, in a comparison of the low-frequency vibrational modes in the resonance Raman spectrum of the heme-HO complex to those of myoglobin, the spectra are found to be very different, indicating that the interactions between the heme and its amino acid pocket in these two proteins are quite different. The neutral imidazole may play several important roles in the physiological function of the heme-HO complex.

出版ステータスPublished - 1994 5月 1

ASJC Scopus subject areas

  • 生化学


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