G proteins - The arginine finger strikes again

Members of the Ras family of G (GTP-binding) proteins play pivotal roles in transmitting signals between the cell surface and the nucleus. They are turned off when GTP is hydrolysed to GDP. But how? Now we know, for three crystal structures reveal the details of the mechanism concerned. A great deal of attention will centre on the work of the groups concerned — for the structures show, at atomic resolution, why mutations in Ras cause 25 per cent of human cancers.