TY - JOUR
T1 - Ligand-protein interactions in nitric oxide synthase
AU - Rousseau, Denis L.
AU - Li, David
AU - Couture, Manon
AU - Yeh, Syun Ru
N1 - Funding Information:
This work was supported by the National Institute of Health Research Grant GM54806 to D.L.R. and HL65465 to S.-R.Y. D.L. is supported by the Medical Scientist Training Program (GM07288) and the Molecular Biophysics Training Grant (GM08572) at Albert Einstein College of Medicine. We thank Dr. Tsuyoshi Egawa and Dr. Jack Peisach of Albert Einstein College of Medicine for many useful discussions, and Dr. Ryu Makino of Rikko University for permission to cite his unpublished data on CPO.
PY - 2005/1
Y1 - 2005/1
N2 - Nitric oxide synthases (NOSs) are heme proteins that catalyze the formation of nitric oxide (NO) from l-arginine and oxygen in a sequential two-step process. Three structurally similar isoforms have been identified that deliver NO to different tissues for specific functions. An understanding of the interactions of ligands with the protein is essential to determine the mechanism of catalysis, the design of inhibitors and the differential auto-inhibitory regulation of the enzymatic activity of the isoforms due to the binding of NO to the heme. Ligand-protein interactions in the three isoforms revealed by resonance Raman scattering studies are reviewed in this article. The CO-related modes in the CO-bound ferrous enzyme are sensitive to the presence of substrate, either l-arginine or N-hydroxy-l-arginine, in the distal pocket, but insensitive to the presence of the tetrahydrobiopterin (H4B) cofactor. In contrast, when NO is coordinated to the ferric heme, the NO is sensitive to the substrate only when H4B is present. Furthermore, in the NO-bound ferric enzyme, the addition of H4B induces a large heme distortion that may modulate heme reduction and thereby regulate the NO auto-inhibitory process. In the metastable O2-bound enzyme, l-arginine binding causes the appearance of a shoulder on the O-O stretching mode, suggesting a specific interaction of the heme-bound dioxygen with the bound-substrate that may be crucial for the oxygenation reaction of the substrate during the catalytic turn-over. It is postulated that spectroscopic differences in the oxy-complex are a consequence of the degree of protonation of the proximal cysteine ligand on the heme. Resonance Raman studies of NOSs expand our understanding of the mechanistic features of this important family of enzymes.
AB - Nitric oxide synthases (NOSs) are heme proteins that catalyze the formation of nitric oxide (NO) from l-arginine and oxygen in a sequential two-step process. Three structurally similar isoforms have been identified that deliver NO to different tissues for specific functions. An understanding of the interactions of ligands with the protein is essential to determine the mechanism of catalysis, the design of inhibitors and the differential auto-inhibitory regulation of the enzymatic activity of the isoforms due to the binding of NO to the heme. Ligand-protein interactions in the three isoforms revealed by resonance Raman scattering studies are reviewed in this article. The CO-related modes in the CO-bound ferrous enzyme are sensitive to the presence of substrate, either l-arginine or N-hydroxy-l-arginine, in the distal pocket, but insensitive to the presence of the tetrahydrobiopterin (H4B) cofactor. In contrast, when NO is coordinated to the ferric heme, the NO is sensitive to the substrate only when H4B is present. Furthermore, in the NO-bound ferric enzyme, the addition of H4B induces a large heme distortion that may modulate heme reduction and thereby regulate the NO auto-inhibitory process. In the metastable O2-bound enzyme, l-arginine binding causes the appearance of a shoulder on the O-O stretching mode, suggesting a specific interaction of the heme-bound dioxygen with the bound-substrate that may be crucial for the oxygenation reaction of the substrate during the catalytic turn-over. It is postulated that spectroscopic differences in the oxy-complex are a consequence of the degree of protonation of the proximal cysteine ligand on the heme. Resonance Raman studies of NOSs expand our understanding of the mechanistic features of this important family of enzymes.
KW - Biophysics
KW - Raman scattering
KW - Vibrational spectroscopy
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U2 - 10.1016/j.jinorgbio.2004.11.007
DO - 10.1016/j.jinorgbio.2004.11.007
M3 - Article
C2 - 15598509
AN - SCOPUS:10444274011
SN - 0162-0134
VL - 99
SP - 306
EP - 323
JO - Journal of Inorganic Biochemistry
JF - Journal of Inorganic Biochemistry
IS - 1
ER -