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Updated: Jul 26, 2026

Measuring Peptide Translocation into Large Unilamellar Vesicles
Published on: January 27, 2012
Peptide mimics as substrates for the intestinal peptide transporter
C S Temple1, A K Stewart, D Meredith
1Department of Human Anatomy, University of Oxford, South Parks Road, Oxford OX1 3QX, United Kingdom.
4-Aminophenylacetic acid (4-APAA), a peptide mimic, is translocated by the proton-linked oligopeptide transporter (PepT1). This finding demonstrates that a peptide bond is not essential for PepT1 substrate translocation.
Area of Science:
- Biochemistry
- Molecular Biology
- Physiology
Background:
- Proton-coupled oligopeptide transporter (PepT1) plays a crucial role in peptide absorption.
- Understanding PepT1 substrate specificity is vital for drug delivery and nutrient transport.
- 4-Aminophenylacetic acid (4-APAA) is a non-peptide molecule with structural similarities to peptides.
Purpose of the Study:
- To investigate the interaction of 4-APAA with the proton-coupled oligopeptide transporter (PepT1).
- To determine if 4-APAA is a substrate for PepT1-mediated transport.
- To explore the structural requirements for PepT1 translocation.
Main Methods:
- High-performance liquid chromatography (HPLC) to quantify 4-APAA transport.
- Fluorimetry using carboxy-SNARF to assess intracellular pH changes in enterocytes.
- Transport assays in isolated rat renal brush-border membrane vesicles.
- Functional studies in Xenopus oocytes expressing PepT1.
Main Results:
- 4-APAA transport across rat intestine was significantly stimulated by luminal acidification.
- 4-APAA application reduced intracellular pH in isolated mouse enterocytes.
- 4-APAA trans-stimulated peptide transport in membrane vesicles and oocytes.
- 4-APAA was confirmed as a substrate for PepT1-mediated translocation.
Conclusions:
- The proton-linked oligopeptide transporter (PepT1) can translocate molecules lacking a peptide bond, such as 4-APAA.
- This study broadens the understanding of PepT1 substrate specificity.
- Further research is needed to define the minimal structural features required for PepT1 translocation.
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