Crystallographic characterization of the membrane-targeting domains of the Rac-specific guanine nucleotide-exchange factors Tiam1 and Tiam2.

T-lymphoma invasion and metastasis 1 and 2 (Tiam1 and Tiam2) are guanine nucleotide-exchange factors that specifically activate Rac GTPase by facilitating the dissociation of GDP. Translocation of Tiam1 and Tiam2 from the cytoplasm to the plasma membrane is an essential step in Rac activation and is mediated by the conserved PH-CC-Ex (pleckstrin-homology, coiled-coil and extra region) region in the N-terminal region. Here, the purification, crystallization and X-ray data collection of the Tiam1 and Tiam2 PH-CC-Ex regions are reported. The regions are shown to exist as a monomer in solution as a folded globular domain. The Tiam2 PH-CC-Ex domain crystallizes in space group P4(1)2(1)2 or P4(3)2(1)2 with four molecules in the asymmetric unit. An X-ray diffraction data set has been collected to 3.2 A resolution.