title: Conformational switching by the scaffolding protein D directs the assembly of bacteriophage phiX174.
abstract: The three-dimensional structure of bacteriophage phiX174 external scaffolding protein D, prior to its interaction with other structural proteins, has been determined to 3.3 angstroms by X-ray crystallography. The crystals belong to space group P4(1)2(1)2 with a dimer in the asymmetric unit that closely resembles asymmetric dimers observed in the phiX174 procapsid structure. Furthermore, application of the crystallographic 4(1) symmetry operation to one of these dimers generates a tetramer similar to the tetramer in the icosahedral asymmetric unit of the procapsid. These data suggest that both dimers and tetramers of the D protein are true morphogenetic intermediates and can form independently of other proteins involved in procapsid morphogenesis. The crystal structure of the D scaffolding protein thus represents the state of the polypeptide prior to procapsid assembly. Hence, comparison with the procapsid structure provides a rare opportunity to follow the conformational switching events necessary for the construction of complex macromolecular assemblies.
authors.affiliation: Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, IN 47907, USA.
authors.forename: Marc C
authors.initials: MC
authors.lastname: Morais
authors.forename: Megan
authors.initials: M
authors.lastname: Fisher
authors.forename: Shuji
authors.initials: S
authors.lastname: Kanamaru
authors.forename: Laralynne
authors.initials: L
authors.lastname: Przybyla
authors.forename: John
authors.initials: J
authors.lastname: Burgner
authors.forename: Bentley A
authors.initials: BA
authors.lastname: Fane
authors.forename: Michael G
authors.initials: MG
authors.lastname: Rossmann
mesh_terms: D010584:Bacteriophage phi X 174 / Q000378:metabolism*; D036022:Capsid Proteins / Q000737:chemistry / Q000378:metabolism; D018360:Crystallography, X-Ray; D019281:Dimerization; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012269:Ribosomal Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D036022:Capsid Proteins; D029968:Escherichia coli Proteins; D012269:Ribosomal Proteins; C425725:ribosome-associated protein SRA, Escherichia coli