title: Topology of the components of the DNA packaging machinery in the phage phi29 prohead.
abstract: Chromosome condensation inside dsDNA viral particles is a complex process requiring the coordinated action of several viral components. The similarity of the process in different viral systems has led to the suggestion that there is a common underlying mechanism for DNA packaging, in which the portal vertex or connector plays a key role. We have studied the topology of the packaging machinery using a number of antibodies directed against different domains of the connector. The charged amino-terminal, the carboxyl-terminal, and the RNA binding domain are accessible areas in the connector assembled into the prohead, while the domains corresponding to the 12 large appendages of the connector are buried inside the prohead. Furthermore, while the antibodies against the carboxyl and amino-terminal do not affect the packaging reaction, incubation of proheads with antibodies against the RNA binding domain abolishes the packaging activity. The comparison of the three-dimensional reconstructions of bacteriophage phi29 proheads with proheads devoid of their specific pRNA by RNase treatment shows that this treatment removes structural elements of the distal vertex of the portal structure, suggesting that the pRNA required for packaging is located at the open gate of the channel in the narrow side of the connector.
authors.affiliation: Department of Macromolecular Structure, Centro Nacional de Biotecnología, CSIC, Campus Universidad Autónoma de Madrid, 28049, Spain.
authors.forename: B
authors.initials: B
authors.lastname: Ibarra
authors.forename: J R
authors.initials: JR
authors.lastname: Castón
authors.forename: O
authors.initials: O
authors.lastname: Llorca
authors.forename: M
authors.initials: M
authors.lastname: Valle
authors.forename: J M
authors.initials: JM
authors.lastname: Valpuesta
authors.forename: J L
authors.initials: JL
authors.lastname: Carrascosa
mesh_terms: D000914:Antibodies, Viral / Q000276:immunology / Q000494:pharmacology; D017103:Bacillus Phages / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure*; D001665:Binding Sites; D002213:Capsid / Q000737:chemistry / Q000276:immunology / Q000378:metabolism / Q000648:ultrastructure*; D036022:Capsid Proteins; D020285:Cryoelectron Microscopy; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000276:immunology; D016253:Microscopy, Immunoelectron; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D012260:Ribonucleases / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism; D019065:Virus Assembly / Q000187:drug effects
chemical_list: D000914:Antibodies, Viral; D036022:Capsid Proteins; D004279:DNA, Viral; D000939:Epitopes; D012367:RNA, Viral; C097975:portal protein, bacteriophage phi29; D012260:Ribonucleases; D012697:Serine Endopeptidases; C028344:glutamyl endopeptidase