Magnesium fluoride-dependent binding of small G proteins to their GTPase-activating proteins

Citation
Dl. Graham et al., Magnesium fluoride-dependent binding of small G proteins to their GTPase-activating proteins, BIOCHEM, 38(45), 1999, pp. 14981-14987
Citations number
34
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biochemistry & Biophysics
Journal title
BIOCHEMISTRY
ISSN journal
0006-2960 → ACNP
Volume
38
Issue
45
Year of publication
1999
Pages
14981 - 14987
Database
ISI
SICI code
0006-2960(19991109)38:45<14981:MFBOSG>2.0.ZU;2-G
Abstract
GTPase-activating proteins (GAPs) enhance the intrinsic GTPase activity of small G proteins, such as Pas and Rho, by contributing a catalytic arginine to the active site. An intramolecular arginine plays a similar role in het erotrimeric G proteins. Aluminum. fluoride activates the GDP form of hetero trimeric G proteins, and enhances binding of the GDP form of small G protei ns to their GAPs. The resultant complexes have been interpreted as analogue s of the transition state of the hydrolytic reaction. Here, equilibrium bin ding has been measured using scintillation proximity assays to provide quan titative information on the fluoride-mediated interaction of Ras and Rile p roteins with their respective GAPs, neurofibromin (NF1) and RhoGAP. High-af finity fluoride-mediated complex formation between Rho . GDP and RhoGAP occ urred in the absence of aluminum; however, under these conditions, magnesiu m was required. Additionally, the novel observation was made of magnesium-d ependent, fluoride-mediated binding of Ras . GDP to NF1 in the absence of a luminum. Aluminum was required for complex formation when the concentration of magnesium was low. Thus, either aluminum:fluoride or magnesium fluoride can mediate the high-affinity binding of Rho . GDP or Ras . GDP to GAPs. I t has been reported that magnesium fluoride can activate heterotrimeric G p roteins. Thus, magnesium-dependent fluoride effects might be a general phen omenon with G proteins. Moreover, these data-suggest that some protein nucl eotide complexes previously reported to contain aluminum fluoride may in fa ct contain magnesium fluoride.