Mechanisms and Functional Properties of Two Peptide Transporters, AtPTR2 and fPTR2

The Arabidopsis AtPTR2 and fungal fPTR2 genes, which encode H + /dipeptide cotransporters, belong to two different subgroups of the p eptide t ransporter ( PTR ) ( NRT1 ) family. In this study, the kinetics, substrate specificity, stoichiometry, and voltage dependence of these two transporters expre...

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Bibliographic Details
Published in:The Journal of biological chemistry 2004-07, Vol.279 (29), p.30150-30157
Main Authors: Chiang, Chien-Sung, Stacey, Gary, Tsay, Yi-Fang
Format: Article
Language:English
Subjects:
Animals
Arabidopsis
Arabidopsis - metabolism
Arabidopsis Proteins - chemistry
Arabidopsis Proteins - physiology
Biological Transport
Cloning, Molecular
DNA, Complementary - metabolism
Electrophysiology
Histidine - chemistry
Humans
Hydrogen-Ion Concentration
Kinetics
Membrane Potentials
Membrane Transport Proteins - chemistry
Membrane Transport Proteins - physiology
Models, Biological
Nitrates - chemistry
Nitrates - metabolism
Oocytes - metabolism
Peptides - chemistry
Phylogeny
Protein Binding
Protein Structure, Tertiary
Saccharomyces cerevisiae Proteins - chemistry
Saccharomyces cerevisiae Proteins - physiology
Substrate Specificity
Xenopus
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Summary:The Arabidopsis AtPTR2 and fungal fPTR2 genes, which encode H + /dipeptide cotransporters, belong to two different subgroups of the p eptide t ransporter ( PTR ) ( NRT1 ) family. In this study, the kinetics, substrate specificity, stoichiometry, and voltage dependence of these two transporters expressed in Xenopus oocytes were investigated using the two-microelectrode voltage-clamp method. The results showed that: 1) although AtPTR2 belongs to the same PTR family subgroup as certain H + /nitrate cotransporters, neither AtPTR2 nor fPTR2 exhibited any nitrate transporting activity; 2) AtPTR2 and fPTR2 transported a wide spectrum of dipeptides with apparent affinity constants in the range of 30 μ m to 3 m m , the affinity being dependent on the side chain structure of both the N- and C-terminal amino acids; 3) larger maximal currents ( I max ) were evoked by positively charged dipeptides in AtPTR2 - or fPTR2 -injected oocytes; 4) a major difference between AtPTR2 and fPTR2 was that, whereas fPTR2 exhibited low Ala-Asp – transporting activity, AtPTR2 transported Ala-Asp – as efficiently as some of the positively charged dipeptides; 5) kinetic analysis suggested that both fPTR2 and AtPTR2 transported by a random binding, simultaneous transport mechanism. The results also showed that AtPTR2 and fPTR2 were quite distinct from PepT1 and PepT2, two well characterized animal PTR transporters in terms of order of binding of substrate and proton(s), pH sensitivity, and voltage dependence.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M405192200