Abstract
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 microM, 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 (3)H-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.
MeSH terms
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Adenosine / biosynthesis
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Adenosine / metabolism*
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Arabidopsis / genetics
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Arabidopsis / metabolism*
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Arabidopsis Proteins / genetics
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Arabidopsis Proteins / metabolism*
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Biological Transport
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Carrier Proteins / genetics
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Carrier Proteins / metabolism*
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Cloning, Molecular
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Equilibrative Nucleoside Transport Proteins / genetics
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Equilibrative Nucleoside Transport Proteins / metabolism*
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Gene Library
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Genetic Complementation Test
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Kinetics
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Membrane Transport Proteins*
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Mutation / genetics
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Nucleoside Transport Proteins
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Nucleosides / metabolism
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / metabolism
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Substrate Specificity
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Time Factors
Substances
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Arabidopsis Proteins
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Carrier Proteins
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ENT1 protein, Arabidopsis
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Equilibrative Nucleoside Transport Proteins
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Membrane Transport Proteins
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Nucleoside Transport Proteins
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Nucleosides
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adenosine transporter
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Adenosine