Expression of the Arabidopsis G-protein GP alpha1: purification and characterisation of the recombinant protein.

The Arabidopsis G alpha subunit, GP alpha1, was expressed within Escherichia coli by co-transformation with the expression vector and the dnaY gene which encodes tRNA(Arg)(AGA/AGG) Isolation of the recombinant GP alpha1 in a highly pure form could be achieved by a combination of anion exchange and dye affinity chromatography or by a single step affinity procedure via chromatography on 4-amino-anilido-GTP agarose. The recombinant protein yielded by both procedures was highly active and bound GTPgammaS with an apparent Kd in the nM range. GTPgammaS binding was stimulated two-fold in the presence of Zn2+ compared with that in the presence of Mg2+, Mn2+ or Ca2+.