Guanine nucleotides and magnesium dependence of the association states of the subunits of transducin |
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Authors: | P Deterre J Bigay C Pfister M Chabre |
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Institution: | Laboratoire de Biologie Moléculaire et Cellulaire (ER 199 CNRS), DRF-CEN-Grenoble, BP 85X F-38041 Grenoble, France |
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Abstract: | When GTP gamma S is bound to transducin (T), the two subunits T alpha X GTP gamma S and T beta gamma dissociate, independently of the ionic environment. When GDP is bound, these subunits are associated as a monomeric T alpha X GDP-T beta gamma complex of 75 kDa when the ionic environment is comparable to that of the cytoplasm, but they dissociate in the presence of 10-100 mM Mg2+ or Ca2+. Using this property, the subunits could be separated and purified by a rapid one-step procedure on an ion-exchange column (FPLC), and their molecular masses were verified by neutron small angle scattering. The physiological relevances of the dissociating effect of Mg2+ are discussed. |
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Keywords: | Transducin GTP-binding protein Magnesium Retinal rod T transducin ROS rod outer segments FPLC fast protein liquid chromatography |
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