GTPASES - A FAMILY OF MOLECULAR SWITCHES AND CLOCKS

Members of the GTPase superfamily share a core domain with a conserved three-dimensional structure and a common GTPase cycle, but perform a wide variety of regulatory tasks in eukaryotic cells. Evolution has cr eated functional diversity from the conserved GTPase structure in two principal ways: (i) by combining in the product of a single gene the c ore GTPase domain attached to one or more additional folded domains; ( ii) by building around a core GTPase an assembly of proteins encoded b y different genes. Analysis of the patterns of conserved amino acid si de chains on surfaces of Ga proteins reveals interfaces with other pro teins in the G-protein signal linking device.