Clarification of the role of protein in carbonmonoxy myoglobin by investigating electronic states
Article first published online: 30 APR 2013
Copyright © 2013 Wiley Periodicals, Inc.
International Journal of Quantum Chemistry
Volume 113, Issue 21, pages 2345–2354, 5 November 2013
How to Cite
How to cite this article: Int. J. Quantum Chem. 2013, 113, 2345–2354. DOI: 10.1002/qua.24459, , , ,
- Issue published online: 23 SEP 2013
- Article first published online: 30 APR 2013
- Manuscript Accepted: 3 APR 2013
- Manuscript Revised: 31 MAR 2013
- Manuscript Received: 15 NOV 2012
- Ministry of Education, Culture, Sports, Science, and Technology (MEXT) for its grants from the program “Research and Development of Next-Generation Integrated Life Simulation Software” and “Research on Innovative Simulation Software” (F.S. and T.H.)
- all-electron density functional calculation • carbonmonoxy myoglobin • distal histidine tautomer • electrostatic potential in heme pocket • size dependence of quantum mechanical region
This article reports the proton tautomerization effects of distal histidine residues in carbonmonoxy myoglobin according to the density functional calculations of the whole protein. The electron eigenstates and electrostatic potential (ESP) distributed around heme and its pocket vary significantly depending on the protonation positions of the distal histidine residues. To investigate the range over which the electronic structures are affected by the proton tautomerization, the quantum mechanics/molecular mechanics (QM/MM) method is applied to probe the QM size to reproduce the atomic partial charges and ESP around the active center. Consequently, we show that these properties converged for the 300 pm QM/MM system in this study. During the analysis, we also find that amino residues such as Phe43, Val68, and Phe138 interact strongly with heme through orbital mixing, indicating that the protein is a medium not only interacting with the reaction center, but also buffering on electrons. © 2013 Wiley Periodicals, Inc.