HEME-HEME OXYGENASE COMPLEX - STRUCTURE AND PROPERTIES OF THE CATALYTIC SITE FROM RESONANCE RAMAN-SCATTERING

被引:96
作者
TAKAHASHI, S
WANG, JL
ROUSSEAU, DL
ISHIKAWA, K
YOSHIDA, T
TAKEUCHI, N
IKEDASAITO, M
机构
[1] AT&T BELL LABS, MURRAY HILL, NJ 07974 USA
[2] YAMAGATA UNIV, SCH MED, DEPT BIOCHEM, YAMAGATA 99023, JAPAN
[3] CASE WESTERN RESERVE UNIV, SCH MED, DEPT PHYSIOL & BIOPHYS, CLEVELAND, OH 44106 USA
关键词
D O I
10.1021/bi00184a023
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
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.
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页码:5531 / 5538
页数:8
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