title: Portal protein functions akin to a DNA-sensor that couples genome-packaging to icosahedral capsid maturation.
abstract: Tailed bacteriophages and herpesviruses assemble infectious particles via an empty precursor capsid (or 'procapsid') built by multiple copies of coat and scaffolding protein and by one dodecameric portal protein. Genome packaging triggers rearrangement of the coat protein and release of scaffolding protein, resulting in dramatic procapsid lattice expansion. Here, we provide structural evidence that the portal protein of the bacteriophage P22 exists in two distinct dodecameric conformations: an asymmetric assembly in the procapsid (PC-portal) that is competent for high affinity binding to the large terminase packaging protein, and a symmetric ring in the mature virion (MV-portal) that has negligible affinity for the packaging motor. Modelling studies indicate the structure of PC-portal is incompatible with DNA coaxially spooled around the portal vertex, suggesting that newly packaged DNA triggers the switch from PC- to MV-conformation. Thus, we propose the signal for termination of 'Headful Packaging' is a DNA-dependent symmetrization of portal protein.
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, Pennsylvania 19107, USA.
authors.forename: Ravi K
authors.initials: RK
authors.lastname: Lokareddy
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, Pennsylvania 19107, USA.
authors.forename: Rajeshwer S
authors.initials: RS
authors.lastname: Sankhala
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, Pennsylvania 19107, USA.|Department of Biochemistry and Molecular Biology, Rutgers University, 683 Hoes lane, Piscataway, New Jersey 08854, USA.
authors.forename: Ankoor
authors.initials: A
authors.lastname: Roy
authors.affiliation: Molecular Biophysics &Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Pavel V
authors.initials: PV
authors.lastname: Afonine
authors.affiliation: Department of Molecular and Cell Biology Department of Chemistry, University of Connecticut, 91N. Eagleville Road, Storrs, Connecticut 06269, USA.
authors.forename: Tina
authors.initials: T
authors.lastname: Motwani
authors.affiliation: Department of Molecular and Cell Biology Department of Chemistry, University of Connecticut, 91N. Eagleville Road, Storrs, Connecticut 06269, USA.
authors.forename: Carolyn M
authors.initials: CM
authors.lastname: Teschke
authors.affiliation: Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Kristin N
authors.initials: KN
authors.lastname: Parent
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, Pennsylvania 19107, USA.|Institute of Biomembranes and Bioenergetics, National Research Council, Via Amendola 165/A, 70126 Bari, Italy.
authors.forename: Gino
authors.initials: G
authors.lastname: Cingolani
mesh_terms: D017100:Bacteriophage P22 / Q000502:physiology* / Q000648:ultrastructure; D002213:Capsid / Q000502:physiology* / Q000648:ultrastructure; D036022:Capsid Proteins / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure; D018360:Crystallography, X-Ray; D042003:DNA Packaging / Q000502:physiology; D004279:DNA, Viral / Q000502:physiology* / Q000648:ultrastructure; D004706:Endodeoxyribonucleases / Q000378:metabolism; D016679:Genome, Viral / Q000502:physiology; D008854:Microscopy, Electron; D062105:Molecular Docking Simulation; D055503:Protein Multimerization / Q000502:physiology; D020836:Protein Structure, Quaternary / Q000502:physiology; D019065:Virus Assembly / Q000502:physiology*
chemical_list: D036022:Capsid Proteins; D004279:DNA, Viral; C079841:portal protein, bacteriophage P22; D004706:Endodeoxyribonucleases; C030894:terminase