Polymer-induced phase separation in aqueous micellar solutions of octyl-β-D-thioglucoside for extraction of membrane proteins
✍ Scribed by Hirofumi Tani; Tohru Saitoh; Tamio Kamidate; Tetsuya Kamataki; Hiroto Watanabe
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 142 KB
- Volume
- 56
- Category
- Article
- ISSN
- 0006-3592
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✦ Synopsis
A water-soluble polymer such as polyethylene glycol (PEG), Dextran T-500 (Dx), or diethylaminoethyl-Dextran (DEAE-Dx) induced aqueous micellar solutions of octyl--D-thioglucoside (OTG) to phase separation at 0°C. One of the two phases thus formed is a surfactantdepleted aqueous solution (aqueous phase) of a watersoluble polymer and the other a concentrated OTG solution (surfactant-rich phase). In a combination of OTG with PEG or Dx, cytochrome P450 (P450) and cytochrome b 5 (b 5 ) were well extracted into the surfactant-rich phase. The extraction yield of P450 was slightly greater than that of b 5 . In contrast to PEG and Dx, DEAE-Dx markedly reduced the extraction of b 5 , while that of P450 remained almost unchanged. DEAE-Dx served the dual functions of inducing the phase separation and preventing the extraction of b 5 into the surfactant-rich phase. This depressed extraction of b 5 was reversed by the addition of potassium phosphate. DEAE-Dx and potassium phosphate proved effective in controlling the extractability of b 5 . The polymer-induced phase separation provides a new basis for highly efficient extraction of membrane proteins under mild conditions that should be acceptable for thermolabile membrane proteins under physiological conditions.