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A molecular basis for NO selectivity in soluble guanylate cyclase
Elizabeth M Boon1, Shirley H Huang, Michael A Marletta
1Department of Chemistry, University of California, Berkeley, California 94720, USA.
Nature Chemical Biology
|January 13, 2006
Summary
Soluble guanylate cyclases (sGCs) are heme sensors that bind nitric oxide (NO). A specific tyrosine residue in H-NOX proteins is crucial for oxygen (O2) binding, enabling selective NO signaling.
Area of Science:
- Biochemistry
- Molecular Biology
- Physiology
Background:
- Soluble guanylate cyclases (sGCs) are heme-containing enzymes critical for NO signaling in animals.
- sGCs belong to the H-NOX (heme nitric oxide/oxygen-binding) protein family, which includes bacterial proteins.
- Differential oxygen (O2) binding affinities in H-NOX proteins explain selective NO signaling in aerobic environments.
Purpose of the Study:
- To elucidate the molecular basis for ligand discrimination in H-NOX proteins.
- To understand how sGCs achieve selective nitric oxide (NO) signaling over oxygen (O2).
Main Methods:
- Utilized a series of wild-type and mutant H-NOX proteins.
- Investigated ligand binding properties, focusing on O2 and NO interactions.
Main Results:
- Identified a distal pocket tyrosine as essential for O2 binding in the H-NOX family.
- Demonstrated that sGCs likely employ kinetic selection against O2 binding.
- Showed that the absence of this tyrosine leads to a rapid O2 dissociation rate, preventing stable O2 complex formation.
Conclusions:
- A distal pocket tyrosine is a key determinant for O2 binding in H-NOX proteins.
- Soluble guanylate cyclases utilize a kinetic mechanism to prevent O2 binding, ensuring NO selectivity.
- This mechanism is vital for precise NO-mediated physiological processes in aerobic organisms.