title: Role of gene 10 protein in the hierarchical assembly of the bacteriophage P22 portal vertex structure.
abstract: The portal vertex structure of the phage P22 is a 2.8 MDa molecular machine that mediates attachment and injection of the viral genome into the host Salmonella enterica serovar Typhimurium. Five proteins form this molecular machine: the portal protein, gp1; the tail-spike, gp9; the tail-needle, gp26, and the tail accessory factors, gp4 and gp10. In order to understand the assembly of the portal vertex structure, we have isolated the gene encoding tail accessory factor gp10 and defined its structural composition and assembly within the portal vertex structure. In solution, monomeric gp10 is a beta-sheet-rich protein with a stable conformational structure, which spontaneously assembles into hexamers, likely via a dimeric intermediate. This oligomerization enhances the structural stability of the protein, which then becomes competent for assembly to a preformed portal protein:gp4 complex, and acts as a structural adaptor bridging the nascent phage tail to gp26 and gp9. Notably, in vitro purified tail accessory factors gp4, gp10, and gp26 do not significantly interact with each other in solution, but their assembly takes place efficiently when these factors are added sequentially onto an immobilized portal protein. This suggests that the assembly of the P22 tail is a highly sequential and cooperative process, likely mediated by structural rearrangements in the assembly components. The assembled portal vertex structure represents both a membrane-binding and penetrating device as well as a plug that retains the pressurized phage DNA inside the capsid.
authors.affiliation: Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, 750 E. Adams Street, Syracuse, New York 13210, USA.
authors.forename: Adam S
authors.initials: AS
authors.lastname: Olia
authors.forename: Anshul
authors.initials: A
authors.lastname: Bhardwaj
authors.forename: Lisa
authors.initials: L
authors.lastname: Joss
authors.forename: Sherwood
authors.initials: S
authors.lastname: Casjens
authors.forename: Gino
authors.initials: G
authors.lastname: Cingolani
mesh_terms: D017100:Bacteriophage P22 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D002152:Calorimetry, Differential Scanning; D036022:Capsid Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D019295:Computational Biology; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D011487:Protein Conformation; D017510:Protein Folding; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012486:Salmonella typhimurium / Q000821:virology; D013696:Temperature; D017376:Viral Tail Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D019065:Virus Assembly
chemical_list: D036022:Capsid Proteins; D011994:Recombinant Proteins; D017376:Viral Tail Proteins; C079841:portal protein, bacteriophage P22