Guanine Nucleotide Dissociation Stimulators

摘要: Small Ras-like GTPases function as bipolar molecular switches to control a variety of cellular processes (Bourne et al. 1991a,b). The cycle between GTP- and GDP-bound states. Evidence from oncogenic mutants Ras identified the GTP-bound form active state, conclusion that has been substantiated by effects dominant negative observations GTP GDP ratio is increased following growth factor or cytokine stimulation cells (e. g., Stacey 1991; Satoh 1991). other similar proteins possess slow intrinsic GTPase activities can be catalytically augmented activating (GAPs) (Trahey McCormick 1987). existence second catalytic which would convert was expected because very low k off for p21 protein (<0.01min−1) in presence physiologically relevant concentrations Mg2+ (Hall Self 1986; Neal 1988). This off-rate lead irreversible accumulation inactive Ras-GDP if no mechanism existed catalyze conversion Ras-GTP state. Mutations confer abnormally high nucleotide release rates can, however, abrogate necessity such activate transforming potential (Lacal Aaronson Feig Cooper 1988b).