Arabidopsis RabE1d subclass plays important plants-pecific functions in plant growth and development, response to ethylene and defence to plant pathogen, besides their basic cellular role in membrane trafficking. In this study, we present the expression, purification, and characterization of the recombinant core domain of AtRabE1d(13-185). AtRabE1d(13-185) was successfully expressed in Escherichia coli and purified via two-step nickel affinity chromatography followed by gel filtration, and identified single band in SDS-PAGE. The resultant protein was functionally active, as determined by interaction with guanine nucleotide by a fluorescencebased assay. The intrinsic tryptophan of AtRabE1d(13-185) showed fluorescence resonance energy transfer (FRET) effect upon forming complex with fluorescent methylanthraniloyl (mant)-GDP, but quenched when binding with non-labelled guanine nucleotide. The association rate of mantGDP with AtRabEld(13-185) was determined to be 3.48 x 10(7) s(-1) M-1. The dissociation rates of GDP and mantGDP from the complex with AtRabE1d(13-185) were similar. The k(off) values were determined to be 4.02 x 10(-4) s(-1) based on the FRET effect for the AtRabE1d(13-185):GDP and 5.41 x 10(-4) s(-1) for mantGDP excited directly. (C) 2015 Elsevier Inc. All rights reserved.