Abstract
AtSUT2 was found to be a low-affinity sucrose transporter (K(M)=11.7 mM at pH 4). Chimeric proteins between AtSUT2 and the high-affinity StSUT1 were constructed in which the extended N-terminus and central loop of AtSUT2 were exchanged with those domains of StSUT1 and vice versa. Chimeras containing the N-terminus of AtSUT2 showed significantly lower affinity for sucrose compared to chimeras containing the N-terminus of StSUT1. The results indicate a significant function of the N-terminus but not the central cytoplasmic loop in determining substrate affinity. Expression of AtSUT2 in major veins of source leaves and in flowers is compatible with a role as a second low-affinity sucrose transporter or as a sucrose sensor.
MeSH terms
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Amino Acid Sequence
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Arabidopsis / chemistry
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Arabidopsis / genetics
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Biological Transport
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Carrier Proteins / chemistry*
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Carrier Proteins / genetics
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Carrier Proteins / metabolism*
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Cytosol / chemistry*
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Gene Expression
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Hydrogen-Ion Concentration
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Kinetics
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Membrane Transport Proteins*
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Molecular Sequence Data
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Peptide Fragments / chemistry
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Peptide Fragments / genetics
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Peptide Fragments / metabolism*
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Plant Proteins / chemistry*
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Plant Proteins / genetics
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Plant Proteins / metabolism*
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Recombinant Fusion Proteins / chemistry
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Recombinant Fusion Proteins / metabolism
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Reverse Transcriptase Polymerase Chain Reaction
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Saccharomyces cerevisiae / genetics
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Sucrose / metabolism
Substances
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Carrier Proteins
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Membrane Transport Proteins
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Peptide Fragments
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Plant Proteins
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Recombinant Fusion Proteins
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sucrose transport protein, plant
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Sucrose