Characterisation of a concentrative type of adenosine transporter from Arabidopsis thaliana (ENT1,At)

Here we report on the isolation, of an Arabidopsis thaliana cDNA that is able to complement a Saccharomyces cerevisiae mutant unable to synthesise adenine. This cDNA encodes a highly hydrophobic protein (ENT1,At) of 428 amino acids, showing high similarity to the human. nucleoside transporter hENT1. Yeast cells expressing ENT1,At are able to grow on adenosine-containing media, adenosine import exhibited an apparent affinity (K-M) of 3.6 muM, and led to accumulation. of this nucleoside within the yeast cell. Transport is inhibited by various nucleosides. Typical inhibitors of ENT-type nucleoside transporters do not inhibit H-3-adenosine import. The presence of protonophores abolished adenosine import, indicating that ENT1,At catalyse a proton-dependent adenosine transport. This is the first functional characterisation of a plant nucleoside transport protein. (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.