FT-infrared spectroscopic studies of the iron ligand CO stretch mode of iNOS oxygenase domain: effect of arginine and tetrahydrobiopterin

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Item Type:	Article
Title:	FT-infrared spectroscopic studies of the iron ligand CO stretch mode of iNOS oxygenase domain: effect of arginine and tetrahydrobiopterin
Creators Name:	Jung, C., Stuehr, D.J. and Ghosh, D.K.
Abstract:	The iron ligand CO stretch vibration mode of the inducible nitric oxide synthase oxygenase domain (iNOSox) has been studied from 20 to 298 K. iNOSox in the absence of arginine reveals a temperature-dependent equilibrium of two major conformational substates with CO stretch bands centered at about 1945 and 1954 cm -1. This behavior is not qualitatively changed when tetrahydrobiopterin (H 4B) is bound. Arginine binding changes significantly the spectrum by formation of a sharp CO stretch mode band at about 1905 cm -1 and indicates the formation of a hydrogen bond to the CO ligand. For temperatures lower than 250 K, the stretch vibration frequency decreases almost linearly with decreasing temperature and indicates that the coupling between the CO ligand and the arginine/protein in the active site via the hydrogen bond is very strong. Flashphotolysis of the CO ligand carried out at 25 K revealed the CO stretch mode of the photodissociated CO ligand trapped in the heme pocket. There is a negative linear relation between the stretch vibration frequencies of the photodissociated and the iron-bound CO indicating that the photodissociated ligand stays near the heme.
Keywords:	Arginine, Biopterin, Carbon Monoxide, Chemical Models, Fourier Transform Infrared Spectroscopy, Hemeproteins, Nitric Oxide Synthase, Nitric Oxide Synthase Type II, Protein Conformation, Recombinant Proteins, Animals, Mice
Source:	Biochemistry
ISSN:	0006-2960
Publisher:	American Chemical Society
Volume:	39
Number:	33
Page Range:	10163-10171
Date:	1 January 2000
Official Publication:	https://doi.org/10.1021/bi0003792
PubMed:	View item in PubMed

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