Membrane proteins are of fundamental importance to cellular processes and nano-encapsulation strategies that preserve their native lipid bilayer environment are particularly attractive for studying and exploiting these proteins. Poly(styrene-co-maleic acid) (SMA) and related polymers poly(styrene-co-(N-(3-N’,N’-dimethylaminopropyl)maleimide)) (SMI) and poly(diisobutylene-alt-maleic acid) (DIBMA) have revolutionised the study of membrane proteins by spontaneously solubilising membrane proteins direct from cell membranes within nanoscale discs of native bilayer called SMA lipid particles (SMALPs), SMILPs and DIBMALPs respectively. This systematic study shows for the first time, that conformational changes of the encapsulated protein are dictated by the solubilising polymer. The photoactivation pathway of rhodopsin (Rho), a G-protein-coupled receptor (GPCR), comprises structurally-defined intermediates with characteristic absorbance spectra that revealed conformational restrictions with styrene-containing SMA and SMI, so that photoactivation proceeded only as far as metarhodopsin-I, absorbing at 478 nm, in a SMALP or SMILP. In contrast, full attainment of metarhodopsin-II, absorbing at 382 nm, was observed in a DIBMALP. Consequently, different intermediate states of Rho could be generated readily by simply employing different SMA-like polymers. Dynamic light-scattering and analytical ultracentrifugation revealed differences in size and thermostability between SMALP, SMILP and DIBMALP. Moreover, encapsulated Rho exhibited different stability in a SMALP, SMILP or DIBMALP. Overall, we establish that SMA, SMI and DIBMA constitute a ‘toolkit’ of solubilising polymers, so that selection of the appropriate solubilising polymer provides a spectrum of useful attributes for studying membrane proteins.
|Pages (from-to)||13519 - 13528|
|Number of pages||10|
|Publication status||Published - 2 Aug 2021|
Bibliographical noteOpen access article. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence CC-BY
FunderThis work was supported by funding from the Biotechnology and Biological Sciences Research Council (BBSRC: BB/ R016615/1 to MW and TRD; BB/R016755/1 to DRP; BB/ S008160/1 to TRD, PJR and MW). RLG was supported by a BBSRC-MIBTP award to RLG and MW. The work in CGT’s laboratory was supported by core funding from the Medical Research Council (MRC U105197215). BK acknowledges support by the South African Research Chairs Initiative of the Department of Science and Technology (DST) and National Research Foundation (NRF) of South Africa (grant no. 46855).
ASJC Scopus subject areas
- Materials Science(all)