Structure of the G60A mutant of Ras: implications for the dominant negative effect.

Substituting alanine for glycine at position 60 in v-H-Ras generated a dominant negative mutant that completely abolished the ability of v-H-Ras to transform NIH 3T3 cells and to induce germinal vesicle breakdown in Xenopus oocytes. The crystal structure of the GppNp-bound form of RasG60A unexpectedly shows that the switch regions adopt an open conformation reminiscent of the structure of the nucleotide-free form of Ras in complex with Sos. Critical residues that normally stabilize the guanine nucleotide and the Mg(2+) ion have moved considerably.

The C-terminal basic tail of RhoG assists the guanine nucleotide exchange factor trio in binding to phospholipids.

The multidomain protein Trio regulates among others neuronal outgrowth and axonal guidance in vertebrates and invertebrates. Trio contains two Dbl-homology/pleckstrin homology (DH/PH) tandem domains that activate several RhoGTPases. Here, we present the x-ray structure of the N-terminal DH/PH, hereafter TrioN, refined to 1.

Crystallization and initial crystal characterization of the N-terminal DH/PH domain of Trio.

Trio is a multidomain signaling protein that plays an important role in neurite outgrowth, axon guidance and skeletal muscle development. Trio contains two DH/PH tandem domains that respectively activate the small GTPases RhoG/Rac and RhoA. The N-terminal DH/PH domain, TrioN, crystallizes in space group P3(1)21, with one TrioN molecule in the asymmetric unit and diffracts to 1.