An amphipathic polypeptide derived from poly‐γ‐glutamic acid for the stabilization of membrane proteins |
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Authors: | Won‐Kyu Lee Dongkook Park Jihye Oh Sung‐Ho Yoon Cheng‐Kang Lee Moon‐Hee Sung Yeon‐Kyun Shin Yeon Gyu Yu |
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Affiliation: | 1. Department of Chemistry, Kookmin University, , Seoul, 136‐702 Republic of Korea;2. Department of Chemical Engineering, National Taiwan University of Science and Technology, , Taipei, 10607 Taiwan;3. Department of Advanced Fermentation Fusion Science and Technology, Kookmin University, , Seoul, 136‐702 Republic of Korea;4. Biomedical Research Institute, Korea Institute of Science and Technology, , Seoul, 136‐791 Republic of Korea;5. Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, , Ames, Iowa, 50011 |
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Abstract: | Difficulties in the extraction of membrane proteins from cell membrane and their solubilization in native conformations have hindered their structural and biochemical analysis. To overcome these difficulties, an amphipathic polypeptide was synthesized by the conjugation of octyl and glucosyl groups to the carboxyl groups of poly‐γ‐glutamic acid (PGA). This polymer, called amphipathic PGA (APG), self‐assembles as mono‐disperse oligomers consisted of 4–5 monomers. APG shows significantly low value of critical micelle concentration and stabilization activity toward membrane proteins. Most of the sodium dodecyl sulfate (SDS)‐solubilized membrane proteins from Escherichia coli remain soluble state in the presence of APG even after the removal of SDS. In addition, APG stabilizes purified 7 transmembrane proteins such as bacteriorhodopsin and human endothelin receptor Type A (ETA) in their active conformations. Furthermore, ETA in complex with APG is readily inserted into liposomes without disrupting the integrity of liposomes. These properties of APG can be applied to overcome the difficulties in the stabilization and reconstitution of membrane proteins. |
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Keywords: | membrane proteins membrane reconstitution G protein‐coupled receptors membrane isolation liposomes plasma membrane detergent |
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