Evidence of Lipid Exchange in Styrene Maleic Acid Lipid Particle (SMALP) Nanodisc Systems

Hazell, Gavin; Arnold, Thomas; Barker, Robert; Clifton, Luke A.; Steinke, Nina‐Juliane; Tognoloni, Cecilia; Edler, Karen J.

doi:10.1021/acs.langmuir.6b02927

Cited by 39 publications

(28 citation statements)

References 57 publications

(90 reference statements)

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“…sphaeroides RCs prepared from membranes lacking both LH1-PufX and LH2 complexes. It should be noted that recent publications on the rapid exchange of lipids in SMALPs suggest that conclusions cannot be drawn on particular lipid enrichment of the target complexes unless they are tightly bound to the protein [48] , [49] . Nevertheless, lipid extracts of bulk chromatophores show a similar lipid profile suggesting SMALP lipids originated from the source membrane and remained associated with the complex during preparation ( Fig.…”

Section: Resultsmentioning

confidence: 99%

Probing the local lipid environment of the cytochrome bc1 and Synechocystis sp. PCC 6803 cytochrome b6f complexes with styrene maleic acid

Swainsbury

Proctor

Hitchcock

et al. 2018

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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Intracytoplasmic vesicles (chromatophores) in the photosynthetic bacterium Rhodobacter sphaeroides represent a minimal structural and functional unit for absorbing photons and utilising their energy for the generation of ATP. The cytochrome bc1 complex (cytbc1) is one of the four major components of the chromatophore alongside the reaction centre-light harvesting 1-PufX core complex (RC-LH1-PufX), the light-harvesting 2 complex (LH2), and ATP synthase. Although the membrane organisation of these complexes is known, their local lipid environments have not been investigated. Here we utilise poly(styrene-alt-maleic acid) (SMA) co-polymers as a tool to simultaneously determine the local lipid environments of the RC-LH1-PufX, LH2 and cytbc1 complexes. SMA has previously been reported to effectively solubilise complexes in lipid-rich membrane regions whilst leaving lipid-poor ordered protein arrays intact. Here we show that SMA solubilises cytbc1 complexes with an efficiency of nearly 70%, whereas solubilisation of RC-LH1-PufX and LH2 was only 10% and 22% respectively. This high susceptibility of cytbc1 to SMA solubilisation is consistent with this complex residing in a locally lipid-rich region. SMA solubilised cytbc1 complexes retain their native dimeric structure and co-purify with 56 ± 6 phospholipids from the chromatophore membrane. We extended this approach to the model cyanobacterium Synechocystis sp. PCC 6803, and show that the cytochrome b6f complex (cytb6f) and Photosystem II (PSII) complexes are susceptible to SMA solubilisation, suggesting they also reside in lipid-rich environments. Thus, lipid-rich membrane regions could be a general requirement for cytbc1/cytb6f complexes, providing a favourable local solvent to promote rapid quinol/quinone binding and release at the Q0 and Qi sites.

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Section: Resultsmentioning

confidence: 99%

Probing the local lipid environment of the cytochrome bc1 and Synechocystis sp. PCC 6803 cytochrome b6f complexes with styrene maleic acid

Swainsbury

Proctor

Hitchcock

et al. 2018

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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“…Studies on ompX have shown an increase in flexibility through changes in detergents [41] . Moreover, it has been shown that the lipids within a SMALP population can interchange, representing a dynamic system [42] , [43] . Although for some systems this may preclude higher resolutions, this may permit a better understanding of the full conformational dynamics of a system.…”

Section: Discussionmentioning

confidence: 99%

Using a SMALP platform to determine a sub-nm single particle cryo-EM membrane protein structure

Parmar

Rawson

Scarff

et al. 2018

Biochimica et Biophysica Acta (BBA) - Biomembranes

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The field of membrane protein structural biology has been revolutionized over the last few years with a number of high profile structures being solved using cryo-EM including Piezo, Ryanodine receptor, TRPV1 and the Glutamate receptor. Further developments in the EM field hold the promise of even greater progress in terms of greater resolution, which for membrane proteins is still typically within the 4–7 Å range. One advantage of a cryo-EM approach is the ability to study membrane proteins in more “native” like environments for example proteoliposomes, amphipols and nanodiscs. Recently, styrene maleic acid co-polymers (SMA) have been used to extract membrane proteins surrounded by native lipids (SMALPs) maintaining a more natural environment. We report here the structure of the Escherichia coli multidrug efflux transporter AcrB in a SMALP scaffold to sub-nm resolution, with the resulting map being consistent with high resolution crystal structures and other EM derived maps. However, both the C-terminal helix (TM12) and TM7 are poorly defined in the map. These helices are at the exterior of the helical bundle and form the greater interaction with the native lipids and SMA polymer and may represent a more dynamic region of the protein. This work shows the promise of using an SMA approach for single particle cryo-EM studies to provide sub-nm structures.

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“…have demonstrated that a membrane protein can readily be transferred from SMALPs to lipidic cubic phases (LCPs) in amounts sufficient for growing well-diffracting crystals. We have reported4 that phospholipids populating the SMALP core can interact and re-associate with large unilamellar vesicles (LUVs), and Edler and co-workers20 have proposed that SMALPs might be able to exchange lipids with monolayers.…”

mentioning

confidence: 99%

Fast Collisional Lipid Transfer Among Polymer-Bounded Nanodiscs

Arenas

Danielczak

Martel

et al. 2017

Sci Rep

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Some styrene/maleic acid (SMA) copolymers solubilise membrane lipids and proteins to form polymer-bounded nanodiscs termed SMA/lipid particles (SMALPs). Although SMALPs preserve a lipid-bilayer core, they appear to be more dynamic than other membrane mimics. We used time-resolved Förster resonance energy transfer and small-angle neutron scattering to determine the kinetics and the mechanisms of phospholipid transfer among SMALPs. In contrast with vesicles or protein-bounded nanodiscs, SMALPs exchange lipids not only by monomer diffusion but also by fast collisional transfer. Under typical experimental conditions, lipid exchange occurs within seconds in the case of SMALPs but takes minutes to days in the other bilayer particles. The diffusional and second-order collisional exchange rate constants for SMALPs at 30 °C are kdif = 0.287 s−1 and kcol = 222 M−1s−1, respectively. Together with the fast kinetics, the observed invariability of the rate constants with probe hydrophobicity and the moderate activation enthalpy of ~70 kJ mol−1 imply that lipids exchange through a “hydrocarbon continuum” enabled by the flexible nature of the SMA belt surrounding the lipid-bilayer core. Owing to their fast lipid-exchange kinetics, SMALPs represent highly dynamic equilibrium rather than kinetically trapped membrane mimics, which has important implications for studying protein/lipid interactions in polymer-bounded nanodiscs.

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Evidence of Lipid Exchange in Styrene Maleic Acid Lipid Particle (SMALP) Nanodisc Systems

Cited by 39 publications

References 57 publications

Probing the local lipid environment of the cytochrome bc1 and Synechocystis sp. PCC 6803 cytochrome b6f complexes with styrene maleic acid

Probing the local lipid environment of the cytochrome bc1 and Synechocystis sp. PCC 6803 cytochrome b6f complexes with styrene maleic acid

Using a SMALP platform to determine a sub-nm single particle cryo-EM membrane protein structure

Fast Collisional Lipid Transfer Among Polymer-Bounded Nanodiscs

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