Abstract
The use of styrene-maleic acid copolymers (SMAs) to produce membrane protein-containing nanodiscs without the initial detergent isolation has gained significant interest over the last decade. We have previously shown that a Photosystem I SMALP from the thermophilic cyanobacterium, Thermosynechococcus elongatus (PSI-SMALP), has much more rapid energy transfer and charge separation in vitro than detergent isolated PSI complexes. In this study, we have utilized small-angle neutron scattering (SANS) to better understand the geometry of these SMALPs. These techniques allow us to investigate the size and shape of these particles in their fully solvated state. Further, the particle's proteolipid core and detergent shell or copolymer belt can be interrogated separately using contrast variation, a capability unique to SANS. Here we report the dimensions of the Thermosynechococcus elongatus PSI-SMALP containing a PSI trimer. At ~1.5 MDa, PSI-SMALP is the largest SMALP to be isolated; our lipidomic analysis indicates it contains ~1300 lipids/per trimeric particle, >40-fold more than the PSI-DDM particle and > 100 fold more than identified in the 1JB0 crystal structure. Interestingly, the lipid composition to the PSI trimer in the PSI-SMALP differs significantly from bulk thylakoid composition, being enriched ~50 % in the anionic sulfolipid, SQDG. Finally, utilizing the contrast match point for the SMA 1440 copolymer, we also can observe the ~1 nm SMA copolymer belt surrounding this SMALP for the first time, consistent with most models of SMA organization.
Original language | English |
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Article number | 148596 |
Journal | Biochimica et Biophysica Acta - Bioenergetics |
Volume | 1863 |
Issue number | 7 |
DOIs | |
State | Published - Oct 1 2022 |
Funding
Support for BDB has been provided from the Gibson Family Foundation , the Dr. Donald L. Akers Faculty Enrichment Fellowship , the Charles P. Postelle Distinguished Professorship . NGB and BDB have been supported via a Joint Directed Research Development Award from University of Tennessee at Knoxville/Oak Ridge National Laboratory Science Alliance , and National Science Foundation ( EPS-1004083 ). NGB has also been supported via a Penley Fellowship . The lipid analyses described in this work were performed at the Kansas Lipidomics Research Center (KLRC) Analytical Laboratory. Instrument acquisition and lipidomics method development were supported by the National Science Foundation (including support from the Major Research Instrumentation program; current award DBI-1726527 ), K-IDeA Networks of Biomedical Research Excellence (INBRE) of National Institute of Health ( P20GM103418 ), USDA National Institute of Food and Agriculture (Hatch/Multi-State project 1013013 ), and Kansas State University . Bio-SANS is part of the Center for Structural Biology at Oak Ridge National Laboratory and is supported by the Office of Biological & Environmental Research (OBER) in the Department of Energy (DOE) Office of Science. This research used resources at the High Flux Isotope Reactor and Spallation Neutron Source, a U.S. Department of Energy Office of Science User Facility operated by ORNL. ORNL is operated by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. Shuo Qian was also partly supported by the Spallation Neutron Source, Second Target Station Project, at Oak Ridge National Laboratory in this project.
Keywords
- Lipidomics
- Photosystem I (PSI)
- Small angle neutron scattering (SANS)
- Styrene maleic acid lipid particle (SMALP)