Engineering a G protein‐coupled receptor for structural studies: Stabilization of the BLT1 receptor ground state

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Abstract
Structural characterization of membrane proteins is hampered by their instability in detergent solutions. We modified here a G protein‐coupled receptor, the BLT1 receptor of leukotriene B4, to stabilize it in vitro. For this, we introduced a metal‐binding site connecting the third and sixth transmembrane domains of the receptor. This modification was intended to restrain the activation‐associated relative movement of these helices that results in a less stable packing in the isolated receptor. The modified receptor binds its agonist with low‐affinity and can no longer trigger G protein activation, indicating that it is stabilized in its ground state conformation. Of importance, the modified BLT1 receptor displays an increased temperature‐, detergent‐, and time‐dependent stability compared with the wild‐type receptor. These data indicate that stabilizing the ground state of this GPCR by limiting the activation‐associated movements of the transmembrane helices is a way to increase its stability in detergent solutions; this could represent a forward step on the way of its crystallization.