title: The NMR-Rosetta capsid model of M13 bacteriophage reveals a quadrupled hydrophobic packing epitope.
abstract: Filamentous phage are elongated semiflexible ssDNA viruses that infect bacteria. The M13 phage, belonging to the family inoviridae, has a length of ∼1 μm and a diameter of ∼7 nm. Here we present a structural model for the capsid of intact M13 bacteriophage using Rosetta model building guided by structure restraints obtained from magic-angle spinning solid-state NMR experimental data. The C5 subunit symmetry observed in fiber diffraction studies was enforced during model building. The structure consists of stacked pentamers with largely alpha helical subunits containing an N-terminal type II β-turn; there is a rise of 16.6-16.7 Å and a tilt of 36.1-36.6° between consecutive pentamers. The packing of the subunits is stabilized by a repeating hydrophobic stacking pocket; each subunit participates in four pockets by contributing different hydrophobic residues, which are spread along the subunit sequence. Our study provides, to our knowledge, the first magic-angle spinning NMR structure of an intact filamentous virus capsid and further demonstrates the strength of this technique as a method of choice to study noncrystalline, high-molecular-weight molecular assemblies.
authors.affiliation: School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv 69978, Tel Aviv, Israel; and.
authors.forename: Omry
authors.initials: O
authors.lastname: Morag
authors.affiliation: Department of Biochemistry, University of Washington, Seattle, WA 98195.
authors.forename: Nikolaos G
authors.initials: NG
authors.lastname: Sgourakis
authors.affiliation: Department of Biochemistry, University of Washington, Seattle, WA 98195.
authors.forename: David
authors.initials: D
authors.lastname: Baker
authors.affiliation: School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv 69978, Tel Aviv, Israel; and amirgo@post.tau.ac.il.
authors.forename: Amir
authors.initials: A
authors.lastname: Goldbourt
mesh_terms: D017104:Bacteriophage M13 / Q000737:chemistry*; D002213:Capsid / Q000737:chemistry*; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D017433:Protein Structure, Secondary
keywords: Rosetta modeling; filamentous bacteriophage; magic-angle spinning; solid-state NMR; structure determination