Title

Pressure Effects On The Proximal Heme Pocket In Myoglobin Probed By Raman And Near-Infrared Absorption Spectroscopy

Authors

Authors

O. Galkin; S. Buchter; A. Tabirian;A. Schulte

Comments

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Abbreviated Journal Title

Biophys. J.

Keywords

MOLECULAR-DYNAMICS SIMULATION; BARRIER HEIGHT DISTRIBUTIONS; CARBON-MONOXIDE BINDING; RESONANCE RAMAN; LIGAND-BINDING; NEUTRON-SCATTERING; BAND-III; PROTEINS; HEMOGLOBIN; SPECTRA; Biophysics

Abstract

The influence of high pressure on the heme protein conformation of myoglobin in different ligation states is studied using Raman spectroscopy over the temperature range from 30 to 295 K. Photostationary experiments monitoring the oxidation state marker bands demonstrate the change of rebinding rate with pressure. While frequency changes of vibrational modes associated with rigid bonds of the porphyrin ring are <1 cm(-1), we investigate a significant shift of the iron-histidine mode to higher frequency with increasing pressure (approximate to 3 cm(-1) for Delta P = 190 MPa in Mb). The observed frequency shift is interpreted structurally as a conformational change affecting the tilt angle between the heme plane and the proximal histidine and the out-of-plane iron position. Independent evidence for iron motion comes from measurements of the redshift of band III in the near-infrared with pressure. This suggests that at high pressure the proximal heme pocket and the protein are altered toward the bound state conformation, which contributes to the rate increase for CO binding. Raman spectra of Mb and photodissociated MbCO measured at low temperature and variable pressure further support changes in protein conformation and are consistent with grasslike properties of myoglobin below 160 K.

Journal Title

Biophysical Journal

Volume

73

Issue/Number

5

Publication Date

1-1-1997

Document Type

Article

Language

English

First Page

2752

Last Page

2763

WOS Identifier

WOS:A1997YD84800049

ISSN

0006-3495

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