Significance of the Molecular Shape of Iron Corrphycene in a Protein Pocket

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• 作者：Saburo Neya ; Kiyohiro Imai ; Yoshitsugu Hiramatsu ; Teizo Kitagawa ; Tyuji Hoshino ; Masayuki Hata ; and Noriaki Funasaki
• 刊名：Inorganic Chemistry
• 出版年：2006
• 出版时间：May 15, 2006
• 年：2006
• 卷：45
• 期：10
• 页码：4238 - 4242
• 全文大小：84K
• 年卷期：v.45,no.10(May 15, 2006)
• ISSN：1520-510X

文摘

The iron complex of a new type of corrphycene bearing two ethoxycarbonyl (-CO₂C₂H₅) groups on the bipyrrolemoiety was introduced into apomyoglobin. The reconstituted ferric myoglobin has a coordinating water moleculethat deprotonates to hydroxide with a pK_a value of 7.3 and exhibits 3-10-fold higher affinities for anionic ligandswhen compared with a counterpart myoglobin with the same substituents on the dipyrroethene moiety. In theferrous state, the oxygen affinity of the new myoglobin was decreased to ¹/₄₁₀ of the native protein. The anomaliesin the ligand binding, notably dependent on the side-chain location, were interpreted in terms of a characteristiccore shape of corrphycene that produces the longer and shorter Fe-N(pyrrole) bonds. The spin-state equilibriumanalysis of the ferric azide myoglobin containing the new iron corrphycene supported the nonequivalence of theFe-N(pyrrole) bonds. These results demonstrate that the trapezoidal molecular shape of corrphycene exerts functionalsignificance when the iron complex is placed in a protein pocket.