Domain families GTPase-mediated signaling pathways

The Ras GTP-mediated activation of P13-kinase links the Ras pathway with fimcti-ons of the Rho/Rac proteins. Members of this protein family within the Ras superfamily control formation of the cytoskeleton. The exact nature of the linkage with the Ras/PI3-kinase signal conduction to the Rac proteins is unknown. There is evidence that the product of the P13-kinase, Ptd-lns(3,4,5)P3, binds to the PH domain of the Vav protein and activates the latter. The Vav protein functions as a nucleotide exchange factor for the Rac GTPase (Han et al., 1998). The observation that activation of the Ras pathway is accompanied by reorganization of the cytoskeleton is in agreement with these findings. 

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