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Biochem J. 2016 Dec 1;473(23):4349-4360. Epub 2016 Sep 30.

Membrane protein extraction and purification using styrene-maleic acid (SMA) copolymer: effect of variations in polymer structure.

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School of Life & Health Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, U.K.
School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K.
College of Medicine, King Saud bin Abdulaziz University for Health Sciences, Jeddah 21423, Kingdom of Saudi Arabia.
Department of Chemistry, University of Warwick, Gibbet Hill, Coventry CV4 7AL, U.K.


The use of styrene-maleic acid (SMA) copolymers to extract and purify transmembrane proteins, while retaining their native bilayer environment, overcomes many of the disadvantages associated with conventional detergent-based procedures. This approach has huge potential for the future of membrane protein structural and functional studies. In this investigation, we have systematically tested a range of commercially available SMA polymers, varying in both the ratio of styrene and maleic acid and in total size, for the ability to extract, purify and stabilise transmembrane proteins. Three different membrane proteins (BmrA, LeuT and ZipA), which vary in size and shape, were used. Our results show that several polymers, can be used to extract membrane proteins, comparably to conventional detergents. A styrene:maleic acid ratio of either 2:1 or 3:1, combined with a relatively small average molecular mass (7.5-10 kDa), is optimal for membrane extraction, and this appears to be independent of the protein size, shape or expression system. A subset of polymers were taken forward for purification, functional and stability tests. Following a one-step affinity purification, SMA 2000 was found to be the best choice for yield, purity and function. However, the other polymers offer subtle differences in size and sensitivity to divalent cations that may be useful for a variety of downstream applications.


SMA; SMALP; membrane proteins; polymer; protein purification; solubilisation

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