title: Detailed architecture of a DNA translocating machine: the high-resolution structure of the bacteriophage phi29 connector particle.
abstract: The three-dimensional crystal structure of the bacteriophage phi29 connector has been solved and refined to 2.1A resolution. This 422 kDa oligomeric protein connects the head of the phage to its tail and translocates the DNA into the prohead during packaging. Each monomer has an elongated shape and is composed of a central, mainly alpha-helical domain that includes a three-helix bundle, a distal alpha/beta domain and a proximal six-stranded SH3-like domain. The protomers assemble into a 12-mer, propeller-like, super-structure with a 35 A wide central channel. The surface of the channel is mainly electronegative, but it includes two lysine rings 20 A apart. On the external surface of the particle a hydrophobic belt extends to the concave area below the SH3-like domain, which forms a crown that retains the particle in the head. The lipophilic belt contacts the non-matching symmetry vertex of the capsid and forms a bearing for the connector rotation. The structure suggests a translocation mechanism in which the longitudinal displacement of the DNA along its axis is coupled to connector spinning.
authors.affiliation: Institut de Biologia Molecular de Barcelona, CSIC, Jordi Girona 18-26, Barcelona, E-08034, Spain. mcccri@ibmb.csic.es
authors.forename: Alicia
authors.initials: A
authors.lastname: Guasch
authors.forename: Joan
authors.initials: J
authors.lastname: Pous
authors.forename: Borja
authors.initials: B
authors.lastname: Ibarra
authors.forename: F Xavier
authors.initials: FX
authors.lastname: Gomis-Rüth
authors.forename: José María
authors.initials: JM
authors.lastname: Valpuesta
authors.forename: Natalia
authors.initials: N
authors.lastname: Sousa
authors.forename: José L
authors.initials: JL
authors.lastname: Carrascosa
authors.forename: Miquel
authors.initials: M
authors.lastname: Coll
mesh_terms: D000595:Amino Acid Sequence; D017103:Bacillus Phages / Q000737:chemistry*; D002213:Capsid / Q000737:chemistry* / Q000378:metabolism*; D036022:Capsid Proteins; D018360:Crystallography, X-Ray; D004279:DNA, Viral / Q000737:chemistry / Q000378:metabolism*; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012399:Rotation; D013329:Structure-Activity Relationship; D019065:Virus Assembly
chemical_list: D036022:Capsid Proteins; D004279:DNA, Viral; C097975:portal protein, bacteriophage phi29