title: Effects of Heme Electronic Structure and Distal Polar Interaction on Functional and Vibrational Properties of Myoglobin.
abstract: We analyzed the oxygen (O2) and carbon monoxide (CO) binding properties, autoxidation reaction rate, and FeO2 and FeCO vibrational frequencies of the H64Q mutant of sperm whale myoglobin (Mb) reconstituted with chemically modified heme cofactors possessing a variety of heme Fe electron densities (ρ(Fe)), and the results were compared with those for the previously studied native [Shibata, T. et al. J. Am. Chem. Soc. 2010, 132, 6091-6098], and H64L [Nishimura, R. et al. Inorg. Chem. 2014, 53, 1091-1099], and L29F [Nishimura, R. et al. Inorg. Chem. 2014, 53, 9156-9165] mutants in order to elucidate the effect of changes in the heme electronic structure and distal polar interaction contributing to stabilization of the Fe-bound ligand on the functional and vibrational properties of the protein. The study revealed that, as in the cases of the previously studied native protein [Shibata, T. et al. Inorg. Chem. 2012, 51, 11955-11960], the O2 affinity and autoxidation reaction rate of the H64Q mutant decreased with a decrease in ρ(Fe), as expected from the effect of a change in ρ(Fe) on the resonance between the Fe(2+)-O2 bond and Fe(3+)-O2(-)-like species in the O2 form, while the CO affinity of the protein is independent of a change in ρ(Fe). We also found that the well-known inverse correlation between the frequencies of Fe-bound CO (ν(CO)) and Fe-C (ν(FeC)) stretching [Li, X.-Y.; Spiro, T. G. J. Am. Chem. Soc. 1988, 110, 6024-6033] is affected differently by changes in ρ(Fe) and the distal polar interaction, indicating that the effects of the two electronic perturbations due to the chemical modification of a heme cofactor and the replacement of nearby amino acid residues on the resonance between the two alternative canonical forms of the FeCO fragment in the protein are slightly different from each other. These findings provide a new insight for deeper understanding of the functional regulation of the protein.
authors.affiliation: Department of Chemistry, University of Tsukuba , Tsukuba 305-8571, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kanai
authors.affiliation: Department of Chemistry, University of Tsukuba , Tsukuba 305-8571, Japan.
authors.forename: Ryu
authors.initials: R
authors.lastname: Nishimura
authors.affiliation: Department of Chemistry, University of Tsukuba , Tsukuba 305-8571, Japan.
authors.forename: Kotaro
authors.initials: K
authors.lastname: Nishiyama
authors.affiliation: Department of Chemistry, University of Tsukuba , Tsukuba 305-8571, Japan.
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Shibata
authors.affiliation: Department of Life Science, Graduate School of Life Science, University of Hyogo, RSC-UH Leading Program Center , Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.
authors.forename: Sachiko
authors.initials: S
authors.lastname: Yanagisawa
authors.affiliation: Department of Life Science, Graduate School of Life Science, University of Hyogo, RSC-UH Leading Program Center , Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Ogura
authors.affiliation: Graduate School of Materials Science, Nara Institute of Science and Technology , Ikoma, Nara 630-0192, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Matsuo
authors.affiliation: Graduate School of Materials Science, Nara Institute of Science and Technology , Ikoma, Nara 630-0192, Japan.
authors.forename: Shun
authors.initials: S
authors.lastname: Hirota
authors.affiliation: Department of Physical Chemistry, Graduate School of Pharmaceutical Sciences, Chiba University , Chuoh-Inohana, Chiba 260-8675, Japan.
authors.forename: Saburo
authors.initials: S
authors.lastname: Neya
authors.affiliation: Department of Materials Engineering, Nagaoka National College of Technology , Nagaoka 940-8532, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Suzuki
authors.affiliation: Department of Chemistry, University of Tsukuba , Tsukuba 305-8571, Japan.|Life Science Center of Tsukuba Advanced Research Alliance, University of Tsukuba , Tsukuba 305-8577, Japan.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Yamamoto
mesh_terms: D006418:Heme / Q000737:chemistry*; D007700:Kinetics; D009211:Myoglobin / Q000737:chemistry*; D066244:Proton Magnetic Resonance Spectroscopy; D013059:Spectrum Analysis, Raman
chemical_list: D009211:Myoglobin; D006418:Heme