Figure 1.

A) Rendering of a model based on the murine mu opioid receptor crystal structure. The side chains of residues computationally designed to generate wsMUR-TM are rendered blue. The root-mean-square deviation of the Cα atoms between this previous comparative model model and the murine structure involving transmembrane domain residues is 2.60Å.⁸ The designed positions selected to be mutated back to the human native identities are shown in magenta (E120T^2.54, K130Y^2.64, D232N^5.36, E297P^6.50, K303I^6.56, G305K^6.58, and K306A^6.59, see Materials and Methods for description about Ballesteros and Weinstein indexing.¹⁰ B) Sequences of the transmembrane domain of wild-type human μ opioid receptor (top) and the designed water-soluble variant wsMUR-TM (bottom) are displayed. Highlighted in orange are the segments of the designed sequence (wsMUR-TM) identified to be important to preserve protein expression. Seven residues that have been restored to native identities are starred and colored in magenta. wsMUR-TM = first variant of the water-soluble human μ opioid receptor transmembrane portion; wsMUR-TM_v2 = modified (second) variant of the water-soluble human μ opioid receptor transmembrane portion; TM = transmembrane; M/Z = mass-to-charge ratio.