title: Assembly of bacteriophage P2 and P4 procapsids with internal scaffolding protein.
abstract: Assembly of the E. coli bacteriophage P2 into an icosahedral capsid with T = 7 symmetry is dependent on the gpN capsid protein, the gpQ connector protein and the gpO internal scaffolding protein. In the presence of the P4-encoded protein Sid, the same proteins are assembled into a smaller capsid with T = 4 symmetry. Although gpO has long been expected to act as an internal scaffolding protein, it has not been possible to produce P2 procapsids efficiently in vitro or in vivo due to a failure to express gpO at high levels. In this study, we find that full-length gpO undergoes proteolytic degradation within 1 h of induction of expression. However, a truncated version of gpO lacking the N-terminal 25 amino acids (Odelta25) is stably expressed at high levels and is able to direct the formation of P2 size procapsids. In the presence of Sid, Odelta25 is incorporated into P4 procapsids, showing that Sid overrides the effect of gpO on capsid size determination.
authors.affiliation: Department of Microbiology, University of Alabama at Birmingham, 845 19th St South, BBRB 311, Birmingham, AL 35294, USA.
authors.forename: Sifang
authors.initials: S
authors.lastname: Wang
authors.forename: Jenny R
authors.initials: JR
authors.lastname: Chang
authors.forename: Terje
authors.initials: T
authors.lastname: Dokland
mesh_terms: D017901:Bacteriophage P2 / Q000502:physiology*; D002213:Capsid / Q000737:chemistry / Q000648:ultrastructure; D036022:Capsid Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000821:virology*; D046529:Microscopy, Electron, Transmission; D017384:Sequence Deletion; D014764:Viral Proteins / Q000032:analysis; D019065:Virus Assembly / Q000502:physiology*
chemical_list: D036022:Capsid Proteins; C095129:Sid protein, Bacteriophage P4; D014764:Viral Proteins