title: Structure and assembly of scalable porous protein cages.
abstract: Proteins that self-assemble into regular shell-like polyhedra are useful, both in nature and in the laboratory, as molecular containers. Here we describe cryo-electron microscopy (EM) structures of two versatile encapsulation systems that exploit engineered electrostatic interactions for cargo loading. We show that increasing the number of negative charges on the lumenal surface of lumazine synthase, a protein that naturally assembles into a ∼1-MDa dodecahedron composed of 12 pentamers, induces stepwise expansion of the native protein shell, giving rise to thermostable ∼3-MDa and ∼6-MDa assemblies containing 180 and 360 subunits, respectively. Remarkably, these expanded particles assume unprecedented tetrahedrally and icosahedrally symmetric structures constructed entirely from pentameric units. Large keyhole-shaped pores in the shell, not present in the wild-type capsid, enable diffusion-limited encapsulation of complementarily charged guests. The structures of these supercharged assemblies demonstrate how programmed electrostatic effects can be effectively harnessed to tailor the architecture and properties of protein cages.
authors.affiliation: Department of Chemistry and Applied Biosciences, Laboratory of Organic Chemistry, ETH Zürich, Zürich 8093, Switzerland.
authors.forename: Eita
authors.identifier: 0000-0002-8202-4465
authors.initials: E
authors.lastname: Sasaki
authors.affiliation: Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zürich, Zürich 8093, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Böhringer
authors.affiliation: Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, CH Utrecht 3584, The Netherlands.
authors.forename: Michiel
authors.initials: M
authors.lastname: van de Waterbeemd
authors.affiliation: Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zürich, Zürich 8093, Switzerland.
authors.forename: Marc
authors.initials: M
authors.lastname: Leibundgut
authors.affiliation: Department of Chemistry and Applied Biosciences, Laboratory of Organic Chemistry, ETH Zürich, Zürich 8093, Switzerland.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Zschoche
authors.affiliation: Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, CH Utrecht 3584, The Netherlands.
authors.forename: Albert J R
authors.initials: AJ
authors.lastname: Heck
authors.affiliation: Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zürich, Zürich 8093, Switzerland.
authors.forename: Nenad
authors.initials: N
authors.lastname: Ban
authors.affiliation: Department of Chemistry and Applied Biosciences, Laboratory of Organic Chemistry, ETH Zürich, Zürich 8093, Switzerland.
authors.forename: Donald
authors.initials: D
authors.lastname: Hilvert
mesh_terms: D001419:Bacteria / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D020285:Cryoelectron Microscopy; D004337:Drug Carriers / Q000737:chemistry*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016062:Porosity; D000072756:Protein Conformation, alpha-Helical; D000072757:Protein Conformation, beta-Strand; D015202:Protein Engineering; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D021122:Protein Subunits / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D055672:Static Electricity
chemical_list: D001426:Bacterial Proteins; D004337:Drug Carriers; D009097:Multienzyme Complexes; D021122:Protein Subunits; D011994:Recombinant Proteins; C044822:6,7-dimethyl-8-ribityllumazine synthase