title: Peering down the barrel of a bacteriophage portal: the genome packaging and release valve in p22.
abstract: The encapsidated genome in all double-strand DNA bacteriophages is packaged to liquid crystalline density through a unique vertex in the procapsid assembly intermediate, which has a portal protein dodecamer in place of five coat protein subunits. The portal orchestrates DNA packaging and exit, through a series of varying interactions with the scaffolding, terminase, and closure proteins. Here, we report an asymmetric cryoEM reconstruction of the entire P22 virion at 7.8 Å resolution. X-ray crystal structure models of the full-length portal and of the portal lacking 123 residues at the C terminus in complex with gene product 4 (Δ123portal-gp4) obtained by Olia et al. (2011) were fitted into this reconstruction. The interpreted density map revealed that the 150 Å, coiled-coil, barrel portion of the portal entraps the last DNA to be packaged and suggests a mechanism for head-full DNA signaling and transient stabilization of the genome during addition of closure proteins.
authors: Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0378, USA.
authors: Jinghua
authors: J
authors: Tang
authors: Gabriel C
authors: GC
authors: Lander
authors: Adam S
authors: AS
authors: Olia
authors: Adam
authors: A
authors: Olia
authors: Rui
authors: R
authors: Li
authors: Sherwood
authors: S
authors: Casjens
authors: Peter
authors: P
authors: Prevelige
authors: Gino
authors: G
authors: Cingolani
authors: Timothy S
authors: TS
authors: Baker
authors: John E
authors: JE
authors: Johnson
mesh_terms: D017100:Bacteriophage P22 / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D036022:Capsid Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics; D016679:Genome, Viral / Q000235:genetics; D008958:Models, Molecular; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D014764:Viral Proteins / Q000737:chemistry / Q000378:metabolism; D014771:Virion / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D019065:Virus Assembly / Q000235:genetics
chemical_list: D036022:Capsid Proteins; D004279:DNA, Viral; D014764:Viral Proteins; C079841:portal protein, bacteriophage P22