title: Significance of the molecular shape of iron corrphycene in a protein pocket.
abstract: The iron complex of a new type of corrphycene bearing two ethoxycarbonyl (-CO2C2H5) groups on the bipyrrole moiety was introduced into apomyoglobin. The reconstituted ferric myoglobin has a coordinating water molecule that deprotonates to hydroxide with a pK(a) value of 7.3 and exhibits 3-10-fold higher affinities for anionic ligands when compared with a counterpart myoglobin with the same substituents on the dipyrroethene moiety. In the ferrous state, the oxygen affinity of the new myoglobin was decreased to 1/410 of the native protein. The anomalies in the ligand binding, notably dependent on the side-chain location, were interpreted in terms of a characteristic core shape of corrphycene that produces the longer and shorter Fe-N(pyrrole) bonds. The spin-state equilibrium analysis of the ferric azide myoglobin containing the new iron corrphycene supported the nonequivalence of the Fe-N(pyrrole) bonds. These results demonstrate that the trapezoidal molecular shape of corrphycene exerts functional significance when the iron complex is placed in a protein pocket.
authors: Department of Physical Chemistry, Graduate School of Pharmaceutical Sciences, Chiba University, Inage-Yayoi, Chiba 263-8522, Japan. sneya@p.chiba-u.ac.jp
authors: Saburo
authors: S
authors: Neya
authors: Kiyohiro
authors: K
authors: Imai
authors: Yoshitsugu
authors: Y
authors: Hiramatsu
authors: Teizo
authors: T
authors: Kitagawa
authors: Tyuji
authors: T
authors: Hoshino
authors: Masayuki
authors: M
authors: Hata
authors: Noriaki
authors: N
authors: Funasaki