Crystallization and preliminary X-ray crystallographic analysis of the receptor-uncoupled mutant of Galphai1.

In order to understand the molecular mechanisms by which G-protein-coupled receptors (GPCRs) activate G proteins, the K349P mutant of Galpha(i1) (K349P), which is unable to couple to the muscarinic acetylcholine receptor, was prepared and its crystals were grown along with those of wild-type Galpha(i1) protein (WT). The two proteins were crystallized under almost identical conditions, thus enabling a detailed structural comparison. The crystallization conditions performed well irrespective of the identity of the bound nucleotide (GDP or GTPgammaS) and the crystals diffracted to resolutions of 2.2 A (WT.GDP), 2.8 A (WT.GTPgammaS), 2.6 A (K349P.GDP) and 3.2 A (K349P.GTPgammaS).