Structural Characterization of the Proximal and Distal Histidine Environment of Cytoglobin and Neuroglobin
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- 作者：Hitomi Sawai ; Masatomo Makino ; Yasuhisa Mizutani ; Takehiro Ohta ; Hiroshi Sugimoto ; Tadayuki Uno ; Norifumi Kawada ; Katsutoshi Yoshizato ; Teizo Kitagawa ; and Yoshitsugu Shiro
- 刊名：Biochemistry
- 出版年：2005
- 出版时间：October 11, 2005
- 年：2005
- 卷：44
- 期：40
- 页码：13257 - 13265
- 全文大小：525K
- 年卷期：v.44,no.40(October 11, 2005)
- ISSN：1520-4995
文摘
Cytoglobin (Cgb) and neuroglobin (Ngb) are the first examples of hexacoordinated globinsfrom humans and other vertebrates in which a histidine (His) residue at the sixth position of the hemeiron is an endogenous ligand in both the ferric and ferrous forms. Static and time-resolved resonanceRaman and FT-IR spectroscopic techniques were applied in examining the structures in the hemeenvironment of these globins. Picosecond time-resolved resonance Raman (ps-TR3) spectroscopy of transientfive-coordinate heme species produced by the photolysis of carbon monoxide (CO) adducts of Cgb andNgb showed Fe-His stretching (
Fe-His) bands at 229 and 221 cm-1, respectively. No time-dependentshift in the Fe-His band of Cgb and Ngb was detected in the 20-1000 ps time domain, in contrast to thecase of myoglobin (Mb). These spectroscopic data, combined with previously reported crystallographicdata, suggest that the structure of the heme pocket in Cgb and Ngb is altered upon CO binding in amanner different from that of Mb and that the scales of the structural alteration are different for Cgb andNgb. The structural property of the heme distal side of the ligand-bound forms was investigated by observingthe sets of (Fe-CO, C-O, 
Fe-C-O) and (Fe-NO, N-O, Fe-N-O) for the CO and nitric oxide (NO) complexesof Cgb and Ngb. A comparison of the spectra of some distal mutants of Cgb (H81A, H81V, R84A,R84K, and R84T) and Ngb (H64A, H64V, K67A, K67R, and K67T) showed that the CO adducts of Cgband Ngb contained three conformers and that the distal His (His81 in Cgb and His64 in Ngb) mainlycontributes to the interconversion of the conformers. These structural characteristics of Cgb and Ngb arediscussed in relation to their ligand binding and physiological properties.
Fe-His) bands at 229 and 221 cm-1, respectively. No time-dependentshift in the Fe-His band of Cgb and Ngb was detected in the 20-1000 ps time domain, in contrast to thecase of myoglobin (Mb). These spectroscopic data, combined with previously reported crystallographicdata, suggest that the structure of the heme pocket in Cgb and Ngb is altered upon CO binding in amanner different from that of Mb and that the scales of the structural alteration are different for Cgb andNgb. The structural property of the heme distal side of the ligand-bound forms was investigated by observingthe sets of (Fe-CO, C-O, Fe-C-O) and (Fe-NO, N-O, Fe-N-O) for the CO and nitric oxide (NO) complexesof Cgb and Ngb. A comparison of the spectra of some distal mutants of Cgb (H81A, H81V, R84A,R84K, and R84T) and Ngb (H64A, H64V, K67A, K67R, and K67T) showed that the CO adducts of Cgband Ngb contained three conformers and that the distal His (His81 in Cgb and His64 in Ngb) mainlycontributes to the interconversion of the conformers. These structural characteristics of Cgb and Ngb arediscussed in relation to their ligand binding and physiological properties.