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Transmembrane aromatic amino acid distribution in P-glycoprotein. A functional role in broad substrate specificity
A B Pawagi1, J Wang, M Silverman
1Department of Medicine, University of Toronto, Ontario, Canada.
Journal of Molecular Biology
|January 14, 1994
Summary
Multidrug resistance in cancer involves P-glycoprotein (Pgp) transporting diverse drugs. Aromatic residues in Pgp
Area of Science:
- Biochemistry
- Molecular Biology
- Cancer Research
Background:
- Multidrug resistance (MDR) in cancer is a major challenge.
- P-glycoprotein (Pgp) overexpression is a key mechanism of MDR.
- Pgp transports a wide range of hydrophobic drugs across cell membranes.
Purpose of the Study:
- To investigate the molecular basis of Pgp's broad substrate specificity.
- To elucidate the structural mechanisms underlying Pgp-mediated drug efflux.
Main Methods:
- Analysis of conserved aromatic amino acid residues in Pgp transmembrane (TM) regions.
- Computer-generated three-dimensional modeling of Pgp structure.
- Simulation of substrate (rhodamine 123) interaction with Pgp models.
Main Results:
- Pgp's TM regions are rich in conserved aromatic residues, particularly phenylalanine.
- Substrates can intercalate within aromatic side-chains, forming a compatible pore for transport.
- The Pgp transport path can be non-polar, utilizing aromatic side-chains or helix-lipid interfaces.
- Weakly polar interactions between drug molecules and aromatic residues contribute to binding.
Conclusions:
- Pgp's broad substrate specificity arises from its adaptable transport pathway.
- Aromatic residues and dynamic reorganization enable Pgp to bind and efflux diverse hydrophobic drugs.
- Understanding Pgp structure-drug interactions is crucial for overcoming MDR in cancer therapy.