Creative Biolabs has spent years of efforts on membrane protein expression and stabilization and successfully established a versatile Magic™ platform that integrates a full portfolio of leading-edge strategies. Our non-stop exploration and dedication has earned us great reputation from our worldwide clients. Currently, our scientists are proud to present our professional service to produce membrane proteins using styrene maleic acid copolymer lipid particles (SMALPs) to meet diverse demands of different research purposes.
Membrane proteins play essential roles in many biological processes. However, to solubilize and stabilize protein targets isolated from the plasma membrane in a native-like environment has always been a great challenge. The detergent used to be a common choice. But improper use of a detergent (i.e. detergent type, concentration, etc.) can lead to protein misfolding, aggregation and denaturation. Hence, it requires an extensive and empirical screening to find the suitable one for each specific case. Proteoliposomes and nanodiscs also present good alternatives, yet can be time- and labor-consuming to prepare. In recent years, styrene maleic acid (SMA) copolymer emerges as a new and promising tool to directly extract and stabilize membrane proteins from cell membrane in the form of polymer-bounded nanodiscs, without additional detergent solubilization steps.
SMA is a low molecular weight amphipathic polymer and a hydrolyzed form of the styrene-maleic anhydride (SMAnh) copolymer (Fig. 1). Styrene is responsible for the hydrophobic characteristic and maleic acid for hydrophilic. The ratio of styrene and maleic acid used in membrane protein solubilization is typically 2:1 or 3:1 with a Mw in the range of 7.5-10 kDa. SMALPs are membrane lipid bilayer surrounded by an outer SMA copolymer annulus.
Fig. 1 Schematic representation of the synthesis of SMAnh (Reaction 1) and SMA (Reaction 2) at a 1:1 ratio. (Dörr, et al., 2016)
SMA can extract membrane proteins from bacteria, yeast, insect and mammalian cells in a concentration of 2%~2.5% (w/v). There are three steps during the solubilization of lipid membranes. First, add SMA copolymer to membrane environment and SMA will bind to the membrane surface followed by the polymer insertion into the membrane at pH 7 to 8. Then, membrane proteins will be solubilized and uniform SMALPs are subsequently formed.
Membrane proteins in SMALPs can then be further purified using standard methods (Fig. 2). The size of SMALPs is uniform, but diameters would vary between 10 and 24 nm depending on different proteins. In particular, for membrane proteins that are relatively difficult to solubilize from membranes caused by tight lipid packing or low lipid/protein ratio, DMPC can be added to enhance the extraction efficiency.
Fig. 2 Extraction of membrane proteins with native lipid environment by SMA. (Dörr, et al., 2016)
The advantage of membrane protein reconstituted in SMALPs including but not limited to:
In addition to membrane protein preparation using SMALPs, Creative Biolabs also offers many other alternatives for different applications and requests:
Please feel free to inquire us for more detailed information.