1. A computationally designed water-soluble variant of a G-protein-coupled receptor: the human mu opioid receptor
- Author
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Jeffery G. Saven, Xu Cui, Felipe Matsunaga, Bernard Selling, Jose Manuel Perez-Aguilar, Renyu Liu, and Jin Xi
- Subjects
Models, Molecular ,Protein Denaturation ,Receptors, Opioid, mu ,Protein Engineering ,Biochemistry ,Protein Structure, Secondary ,0302 clinical medicine ,Protein structure ,Computational Chemistry ,Anesthesiology ,Molecular Cell Biology ,Urea ,Signaling in Cellular Processes ,Protein secondary structure ,Peptide sequence ,0303 health sciences ,Multidisciplinary ,Chemistry ,Protein Stability ,Transmembrane protein ,Solutions ,Transmembrane domain ,Neurology ,Reducing Agents ,Computer-Aided Design ,Medicine ,Research Article ,Signal Transduction ,Science ,Molecular Sequence Data ,Biophysics ,Anesthetic Mechanisms ,Binding, Competitive ,Protein Chemistry ,03 medical and health sciences ,Neuropharmacology ,Escherichia coli ,Humans ,Pain Management ,Amino Acid Sequence ,Biology ,030304 developmental biology ,G protein-coupled receptor ,Mercaptoethanol ,Computational Biology ,Water ,Proteins ,Protein engineering ,Protein Structure, Tertiary ,G-Protein Signaling ,HEK293 Cells ,Membrane protein ,Amino Acid Substitution ,Solubility ,030217 neurology & neurosurgery - Abstract
G-protein-coupled receptors (GPCRs) play essential roles in various physiological processes, and are widely targeted by pharmaceutical drugs. Despite their importance, studying GPCRs has been problematic due to difficulties in isolating large quantities of these membrane proteins in forms that retain their ligand binding capabilities. Creating water-soluble variants of GPCRs by mutating the exterior, transmembrane residues provides a potential method to overcome these difficulties. Here we present the first study involving the computational design, expression and characterization of water-soluble variant of a human GPCR, the human mu opioid receptor (MUR), which is involved in pain and addiction. An atomistic structure of the transmembrane domain was built using comparative (homology) modeling and known GPCR structures. This structure was highly similar to the subsequently determined structure of the murine receptor and was used to computationally design 53 mutations of exterior residues in the transmembrane region, yielding a variant intended to be soluble in aqueous media. The designed variant expressed in high yield in Escherichia coli and was water soluble. The variant shared structural and functionally related features with the native human MUR, including helical secondary structure and comparable affinity for the antagonist naltrexone (K d = 65 nM). The roles of cholesterol and disulfide bonds on the stability of the receptor variant were also investigated. This study exemplifies the potential of the computational approach to produce water-soluble variants of GPCRs amenable for structural and functionally related characterization in aqueous solution.
- Published
- 2013