TY - JOUR
T1 - Interactions of CuB with Carbon Monoxide in Cytochrome c Oxidase
T2 - Origin of the Anomalous Correlation between the Fe-CO and C-O Stretching Frequencies
AU - Egawa, Tsuyoshi
AU - Haber, Jonah
AU - Fee, James A.
AU - Yeh, Syun Ru
AU - Rousseau, Denis L.
N1 - Publisher Copyright:
© 2015 American Chemical Society.
PY - 2015/7/9
Y1 - 2015/7/9
N2 - In heme-copper oxidases, the correlation curve between the iron-CO and C-O stretching vibrational modes (νFe-CO and νC-O, respectively) is anomalous as compared to the correlation in other heme proteins. To extend the correlation curve, the resonance Raman (RR) and infrared (IR) spectra of the CO adducts of cytochrome ba3 (ba3) from Thermus thermophilus were measured. The RR spectrum has two strong νFe-CO lines (508 and 515 cm-1) and a very weak line at 526 cm-1, and the IR spectrum has three νC-O lines (1966, 1973, and 1981 cm-1), indicating the presence of multiple conformers. Employing photodissociation methods, the νFe-CO RR and νC-O IR lines were assigned to each conformer, enabling the establishment of a reliable inverse correlation curve for the νFe-CO versus the νC-O stretching frequencies. To determine the molecular basis of the correlation, a series of DFT calculations on 6-coordinate porphyrin-CO compounds and a model of the binuclear center of the heme-copper oxidases were carried out. The calculations demonstrated that the copper unit model caused significant mixing among porphyrin-CO molecular orbitals (MOs) that contribute to the Fe-C and C-O bonding interactions, and also indicated the presence of mixing between the dz2 orbital of the copper and MOs that are responsible for the νFe-CO vs νC-O inverse correlation. Together, the spectroscopic and DFT results clarify the origin of the anomaly of νFe-CO and νC-O frequencies in the heme-copper oxidases, a long-standing issue. (Graph Presented).
AB - In heme-copper oxidases, the correlation curve between the iron-CO and C-O stretching vibrational modes (νFe-CO and νC-O, respectively) is anomalous as compared to the correlation in other heme proteins. To extend the correlation curve, the resonance Raman (RR) and infrared (IR) spectra of the CO adducts of cytochrome ba3 (ba3) from Thermus thermophilus were measured. The RR spectrum has two strong νFe-CO lines (508 and 515 cm-1) and a very weak line at 526 cm-1, and the IR spectrum has three νC-O lines (1966, 1973, and 1981 cm-1), indicating the presence of multiple conformers. Employing photodissociation methods, the νFe-CO RR and νC-O IR lines were assigned to each conformer, enabling the establishment of a reliable inverse correlation curve for the νFe-CO versus the νC-O stretching frequencies. To determine the molecular basis of the correlation, a series of DFT calculations on 6-coordinate porphyrin-CO compounds and a model of the binuclear center of the heme-copper oxidases were carried out. The calculations demonstrated that the copper unit model caused significant mixing among porphyrin-CO molecular orbitals (MOs) that contribute to the Fe-C and C-O bonding interactions, and also indicated the presence of mixing between the dz2 orbital of the copper and MOs that are responsible for the νFe-CO vs νC-O inverse correlation. Together, the spectroscopic and DFT results clarify the origin of the anomaly of νFe-CO and νC-O frequencies in the heme-copper oxidases, a long-standing issue. (Graph Presented).
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U2 - 10.1021/acs.jpcb.5b04444
DO - 10.1021/acs.jpcb.5b04444
M3 - Article
C2 - 26056844
AN - SCOPUS:84937046319
SN - 1520-6106
VL - 119
SP - 8509
EP - 8520
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 27
ER -