Composition of raft-like cell membrane microdomains resistant to styrene-maleic acid copolymer (SMA) solubilization

An advantageous alternative to the use of detergents in biochemical studies on membrane proteins are the recently developed styrene-maleic acid (SMA) amphipathic copolymers. In our recent study [1] we demonstrated that using this approach, most T cell membrane proteins were fully solubilized (presumably in small nanodiscs), while two types of raft proteins, GPI-anchored proteins and Src family kinases, were mostly present in much larger (>250 nm) membrane fragments markedly enriched in typical raft lipids, cholesterol and lipids containing saturated fatty acid residues. In the present study we demonstrate that disintegration of membranes of several other cell types by means of SMA copolymer follows a similar pattern and we provide a detailed proteomic and lipidomic characterization of these SMA-resistant membrane fragments (SRMs).

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English Summary: The styrene-maleic acid (SMA) amphipathic copolymers have emerged as a beneficial alternative to detergents for studying membrane proteins. In our recent study, we found that most T cell membrane proteins were soluble in small nanodiscs using this method, while raft proteins, specifically GPI-anchored proteins and Src family kinases, were present in larger membrane fragments enriched in raft lipids. Our present study further confirms this pattern of membrane disintegration by SMA copolymer in other cell types and provides a detailed characterization of these SMA-resistant membrane fragments (SRMs) at the proteomic and lipidomic levels.