Structural mechanism for lipid activation of the Rac-specific GAP, beta2-chimaerinGTPase-activating protein

The crystal structure at 3.2 angstron unit resolution of one such protein, beta 2-chimaerin, a GTPase-activating protein for the small GTPase Rac, in its inactive conformation is reported. The structure shows that in the inactive state, the N terminus of beta2-chimaerin protrudes into the inactive site of the RacGAP domain, sterically blocking Rac binding.