The Extracellular pH Dependency of Transport Activity by Human Oligopeptide Transporter 1 (hPEPT1) Expressed Stably in Chinese Hamster Ovary (CHO) Cells: A Reason for the Bell-Shaped Activity versus pH
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- Fujisawa Yuki
- Laboratory of Biophysical Chemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University
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- Tateoka Ryoko
- Laboratory of Biophysical Chemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University
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- Nara Toshifumi
- Laboratory of Biophysical Chemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University
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- Kamo Naoki
- Laboratory of Biophysical Chemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University
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- Taira Takahiro
- Molecular Biology, Graduate School of Pharmaceutical Sciences, Hokkaido University
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- Miyauchi Seiji
- Laboratory of Biophysical Chemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University
書誌事項
- タイトル別名
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- Extracellular pH Dependency of Transport Activity by Human Oligopeptide Transporter 1 hPEPT1 Expressed Stably in Chinese Hamster Ovary CHO Cells A Reason for the Bell Shaped Activity versus pH
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Human oligopeptide transporter (hPEPT1) translocates di/tri-peptide by coupling to movement of proton down the electrochemical gradient. This transporter has the characteristics that the pH-profile of neutral dipeptide transport shows a bell-shaped curve with an optimal pH of 5.5. In the present study, we examined the reason for the decrease in the acidic region with hPEPT1-transfected CHO cells stably oeverexpressing hPEPT1 (CHO/hPEPT1). The pH profile of the transport activity vs. pH was measured in the presence of nigericin/monensin. Under this condition, the inwardly directed proton concentration gradient was dissipated while the membrane potential remained. As pH increased the activity increased, and the Henderson–Hasselbalch equation with a single pKa was fitted well to the activity curve. The pKa value was estimated to be 6.7±0.2. This value strongly suggests that there is a key amino acid residue, which is involved in pH regulation of transport activity. To identify the key amino acid residue, we examined the effects of various chemical modifications on pH-profile of the transport activity. Modification of carboxyl groups or hydroxyl groups had no significant influence on the pH-profile, whereas a chemical modification of histidine residue with diethylpyrocarbonate (DEPC) completely abolished the transport activity in CHO/hPEPT1 cells. On the other hand, this abolishment was almost prevented by the presence of 10 mM Gly-Sar. This protection was observed only in the presence of the substrate of hPEPT1, indicating that the histidine residue is located at the substrate recognition site. The pH-profile of the transport activity in CHO/hPEPT1 cells treated with DEPC in the presence of 10 mM Gly-Sar also showed a bell-shape similar to that in non-treated CHO/hPEPT1 cells. These data stressed that the histidine residue located at or near the substrate binding site is involved in the pH regulation of transport activity.
収録刊行物
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- Biological & Pharmaceutical Bulletin
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Biological & Pharmaceutical Bulletin 29 (5), 997-1005, 2006
公益社団法人 日本薬学会
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詳細情報 詳細情報について
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- CRID
- 1390282679601229440
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- NII論文ID
- 110005602229
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- NII書誌ID
- AA10885497
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- ISSN
- 13475215
- 09186158
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- NDL書誌ID
- 7892683
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- 本文言語コード
- en
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- データソース種別
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- JaLC
- NDL
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