Title

Pressure effects on the proximal heme pocket in myoglobin probed by Raman and near-infrared absorption spectroscopy

Abstract

The influence of high pressure on the heme protein conformation of myoglobin in different ligation states is studied using Raman spectroscopy ever 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 (≃3 cm-1 for ΔP = 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 glasslike properties of myoglobin below 160 K.

Publication Date

1-1-1997

Publication Title

Biophysical Journal

Volume

73

Issue

5

Number of Pages

2752-2763

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1016/S0006-3495(97)78304-8

Socpus ID

0030834054 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/0030834054

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