Iron Hemiporphycene as a Functional Prosthetic Group for Myoglobin
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- 作者：Saburo Neya ; Kiyohiro Imai ; Hiroshi Hori ; Haruto Ishikawa ; Koichiro Ishimori ; Daichi Okuno ; Shigenori Nagatomo ; Tyuji Hoshino ; Masayuki Hata ; and Noriaki Funasaki
- 刊名：Inorganic Chemistry
- 出版年：2003
- 出版时间：March 10, 2003
- 年：2003
- 卷：42
- 期：5
- 页码：1456 - 1461
- 全文大小：119K
- 年卷期：v.42,no.5(March 10, 2003)
- ISSN：1520-510X
文摘
The iron complex of hemiporphycene, a molecular hybrid of porphyrin with porphycene, was incorporated into theapomyoglobin pocket to examine ligand binding ability of the iron atom in the novel porphyrinoid. Apomyoglobinwas successfully coupled with a stoichiometric amount of ferric hemiporphycene to afford the reconstituted myoglobinequipped with the iron coordination structure of native protein. Cyanide, imidazole, and fluoride coordinated to theferric protein with affinities comparable with those for native myoglobin. The ferrous myoglobin was functionallyactive to bind O2 and CO reversibly at pH 7.4 and 20 
C. The O2 affinity is 12-fold higher than that of nativemyoglobin while the CO affinity is slightly lower, suggesting decreased discrimination between O2 and CO in theheme pocket. The functional anomaly was interpreted to reflect increased 
-bonding character in the Fe(II)-O2bond. In contrast with 6-coordinate native NO protein, the NO myoglobin containing ferrous hemiporphycene is ina mixed 5- and 6-coordinate state. This observation suggests that the in-plane configuration of the iron atom inhemiporphycene is destabilized by NO. Influence of the core deformation was also detected with both the infraredabsorption for the ferrous CO derivative and electron paramagnetic resonance for ferric imidazole complex. Anomaliesin the ferric and ferrous derivatives were ascribed to the modified iron-N(pyrrole) interactions in the asymmetricmetallo core of hemiporphycene.
C. The O2 affinity is 12-fold higher than that of nativemyoglobin while the CO affinity is slightly lower, suggesting decreased discrimination between O2 and CO in theheme pocket. The functional anomaly was interpreted to reflect increased -bonding character in the Fe(II)-O2bond. In contrast with 6-coordinate native NO protein, the NO myoglobin containing ferrous hemiporphycene is ina mixed 5- and 6-coordinate state. This observation suggests that the in-plane configuration of the iron atom inhemiporphycene is destabilized by NO. Influence of the core deformation was also detected with both the infraredabsorption for the ferrous CO derivative and electron paramagnetic resonance for ferric imidazole complex. Anomaliesin the ferric and ferrous derivatives were ascribed to the modified iron-N(pyrrole) interactions in the asymmetricmetallo core of hemiporphycene.