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FEBS Lett. 1995 Apr 10;362(3):286-90.

The small G-protein ARF1GDP binds to the Gt beta gamma subunit of transducin, but not to Gt alpha GDP-Gt beta gamma.

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CNRS, Institut de Pharmacologie Mol├ęculaire et Cellulaire, Valbonne, France.


AlF4- activates heterotrimeric G-proteins G alpha subunits but not small GDP/GTP-binding proteins like ARF1. On retinal membranes containing holotransducin (Gt alpha GDP-Gt beta gamma) and incubated with ARFGDP, AlF4- induced Gt alpha GDP-AlF4 release and ARFGDP binding, probably to the remaining membrane-attached Gt beta gamma. On phospholipid vesicles reconstituted with Gt beta gamma, ARFGDP bound in proportion to Gt beta gamma, and was released upon subsequent Gt alpha GDP addition. Thus ARFGDP competes with Gt alpha GDP for binding to Gt beta gamma, probably through a conserved motif in the 'alpha 2 helix' of Gt alpha and ARF. This motif is found in the C-terminal helix of PH domains that bind to G beta gamma.

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