Crystallization and preliminary X-ray crystallographic analysis of the receptor-uncoupled mutant of Gα{sub i1}

The K349P mutant of Gα{sub i1}, which is unable to couple to G-protein-coupled receptors, has been crystallized and analyzed. The same crystallization conditions were applicable irrespective of the identity of the bound nucleotide or of the presence of the mutation. In order to understand the molecular mechanisms by which G-protein-coupled receptors (GPCRs) activate G proteins, the K349P mutant of Gα{sub 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 Gα{sub 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 GTPγS) and the crystals diffracted to resolutions of 2.2 Å (WT·GDP), 2.8 Å (WT·GTPγS), 2.6 Å (K349P·GDP) and 3.2 Å (K349P·GTPγS)