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The Journal of Biochemistry
Year: 2009  |  Volume: 146  |  Issue: 6  |  Page No.: 875 - 880

GDP-GTP Exchange Processes of G{alpha}i1 Protein are Accelerated/Decelerated Depending on the Type and the Concentration of Added Detergents

M Kubota, T Tanaka, T Kohno and K. Wakamatsu    

Abstract:

Although detergents have been widely used in G-protein studies to increase solubility and stability of the protein, we noticed that detergents modulate the nucleotide-binding properties of G-proteins. Hence, we analysed the effects of detergents on guanine nucleotide exchange reactions of Gi1. Lubrol PX, a non-ionic detergent, which has been widely used in nucleotide dissociation/binding assays, was found to accelerate both GDP dissociation and GTPS binding from/to G in parallel at above its critical micelle concentration (cmc). Sodium cholate, an anionic detergent, which have been used to extract G-proteins from animal tissues, decelerated and accelerated GDP dissociation below and above its cmc, respectively. Surprisingly, micellar cholate decelerated GTPS binding, and the binding rate constant was decreased by three orders of magnitude in the presence of 2% cholate. These results demonstrate that the guanine nucleotide exchange reactions of Gi1 are drastically modulated by detergents differently depending on the type and the state (monomeric or micellar) of the detergents and that dissociation of GDP from Gi1 does not necessarily lead to immediate binding of GTP to Gi1 in some cases. These effects of detergents on G-proteins must be taken into account in G-protein experiments.

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