title: A saposin-lipoprotein nanoparticle system for membrane proteins.
abstract: A limiting factor in membrane protein research is the ability to solubilize and stabilize such proteins. Detergents are used most often for solubilizing membrane proteins, but they are associated with protein instability and poor compatibility with structural and biophysical studies. Here we present a saposin-lipoprotein nanoparticle system, Salipro, which allows for the reconstitution of membrane proteins in a lipid environment that is stabilized by a scaffold of saposin proteins. We demonstrate the applicability of the method on two purified membrane protein complexes as well as by the direct solubilization and nanoparticle incorporation of a viral membrane protein complex from the virus membrane. Our approach facilitated high-resolution structural studies of the bacterial peptide transporter PeptTSo2 by single-particle cryo-electron microscopy (cryo-EM) and allowed us to stabilize the HIV envelope glycoprotein in a functional state.
authors.affiliation: Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Jens
authors.initials: J
authors.lastname: Frauenfeld
authors.affiliation: Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden.
authors.forename: Robin
authors.initials: R
authors.lastname: Löving
authors.affiliation: Keck Advanced Microscopy Laboratory, Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA.
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Armache
authors.affiliation: Structural and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Heidelberg, Germany.|Molecular Medicine Partnership Unit, European Molecular Biology Laboratory-Universitätsklinikum Heidelberg, Heidelberg, Germany.
authors.forename: Andreas F-P
authors.initials: AF
authors.lastname: Sonnen
authors.affiliation: Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Fatma
authors.initials: F
authors.lastname: Guettou
authors.affiliation: Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Moberg
authors.affiliation: Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden.|School of Technology and Health, Royal Institute of Technology, Novum, Huddinge, Sweden.
authors.forename: Lin
authors.initials: L
authors.lastname: Zhu
authors.affiliation: Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden.|School of Technology and Health, Royal Institute of Technology, Novum, Huddinge, Sweden.
authors.forename: Caroline
authors.initials: C
authors.lastname: Jegerschöld
authors.affiliation: EMBL Hamburg, Hamburg, Germany.
authors.forename: Ali
authors.initials: A
authors.lastname: Flayhan
authors.affiliation: Structural and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Heidelberg, Germany.|Molecular Medicine Partnership Unit, European Molecular Biology Laboratory-Universitätsklinikum Heidelberg, Heidelberg, Germany.
authors.forename: John A G
authors.initials: JA
authors.lastname: Briggs
authors.affiliation: Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden.
authors.forename: Henrik
authors.initials: H
authors.lastname: Garoff
authors.affiliation: Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.|EMBL Hamburg, Hamburg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Löw
authors.affiliation: Keck Advanced Microscopy Laboratory, Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA.|Howard Hughes Medical Institute, University of California San Francisco, San Francisco, California, USA.
authors.forename: Yifan
authors.initials: Y
authors.lastname: Cheng
authors.affiliation: Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Pär
authors.initials: P
authors.lastname: Nordlund
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D020285:Cryoelectron Microscopy / Q000379:methods; D015699:HIV Envelope Protein gp120 / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D008055:Lipids / Q000737:chemistry*; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D053758:Nanoparticles / Q000737:chemistry*; D011487:Protein Conformation; D049231:Saposins / Q000737:chemistry* / Q000378:metabolism; D027981:Symporters / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D015699:HIV Envelope Protein gp120; D008055:Lipids; D008565:Membrane Proteins; D049231:Saposins; D027981:Symporters; C093694:hydrogen-coupled oligopeptide transporter PepT2