Functional Roles of Histidine and Tyrosine Residues in the H+-Peptide Transporter PepT1
| Autor: | Angela Steel, Matthias A. Hediger, Xing-Zhen Chen |
|---|---|
| Rok vydání: | 2000 |
| Předmět: |
Mutant
Biophysics Xenopus Peptide Biology Models Biological Peptide Transporter 1 Biochemistry Substrate Specificity Xenopus laevis Diethyl Pyrocarbonate Animals Histidine Tyrosine Molecular Biology chemistry.chemical_classification Base Sequence Symporters Mutagenesis Biological Transport Transporter Dipeptides Cell Biology Hydrogen-Ion Concentration biology.organism_classification Transmembrane protein Kinetics Amino Acid Substitution chemistry Mutation Oocytes Rabbits Protons Carrier Proteins |
| Zdroj: | Biochemical and Biophysical Research Communications. 272:726-730 |
| ISSN: | 0006-291X |
| DOI: | 10.1006/bbrc.2000.2851 |
| Popis: | Histidyl residues in peptide transporters PepT1 and PepT2 are believed to participate in proton and substrate binding and to be crucial to the transporters' functional activities. In the present study, we performed mutagenesis of rabbit PepT1. We mutated three histidine residues (H57, H111, and H121) predicted to reside in transmembrane segments, as well as tyrosine residues adjacent to H57. Functional analysis of wild-type and mutant PepT1 expressed in Xenopus oocytes, using both the radiotracer methods and two-microelectrode voltage-clamping, revealed that not only the H57 but also the aromatic residues near H57 were essential for the normal function of PepT1, in agreement with the concept that aromatic residues stabilize the charge on H+ when interacting with H57. While mutagenesis at H111 did not significantly affect the activity of PepT1, mutagenesis at H121 had profound implications. The substrate affinities for H121 mutants were decreased depending both on the charge of the substrate and the charge on the substituted residues at position 121. We propose that H57 and H121 are intimately involved in the binding of the coupling ion H+ and the recognition of transportable peptide substrates, respectively. |
| Databáze: | OpenAIRE |
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