title: Purification and functional characterization of p16, the ATPase of the bacteriophage Phi29 packaging machinery.
abstract: Bacteriophage Phi29 codes for a protein (p16) that is required for viral DNA packaging both in vivo and in vitro. Co-expression of p16 with the chaperonins GroEL and GroES has allowed its purification in a soluble form. Purified p16 shows a weak ATPase activity that is stimulated by either DNA or RNA, irrespective of the presence of any other viral component. The stimulation of ATPase activity of p16, although induced under packaging conditions, is not dependent of the actual DNA packaging and in this respect the Phi29 enzyme is similar to other viral terminases. Protein p16 competes with DNA and RNA in the interaction with the viral prohead, which occurs through the N-terminal region of the connector protein (p10). In fact, p16 interacts in a nucleotide-dependent fashion with the viral Phi29-encoded RNA (pRNA) involved in DNA packaging, and this binding can be competed with DNA. Our results are consistent with a model for DNA translocation in which p16, bound and organized around the connector, acts as a power stroke to pump the DNA into the prohead, using the hydrolysis of ATP as an energy source.
authors.affiliation: Department of Macromolecular Structure, Centro Nacional de Biotecnología (CSIC), Campus de la Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
authors.forename: B
authors.initials: B
authors.lastname: Ibarra
authors.forename: J M
authors.initials: JM
authors.lastname: Valpuesta
authors.forename: J L
authors.initials: JL
authors.lastname: Carrascosa
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D017103:Bacillus Phages / Q000201:enzymology* / Q000235:genetics; D001412:Bacillus subtilis / Q000821:virology; D018835:Chaperonin 10 / Q000235:genetics / Q000378:metabolism; D018834:Chaperonin 60 / Q000235:genetics / Q000378:metabolism; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D006868:Hydrolysis; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism; D012995:Solubility; D015678:Viral Structural Proteins / Q000235:genetics / Q000378:metabolism; D019065:Virus Assembly
chemical_list: D018835:Chaperonin 10; D018834:Chaperonin 60; D004279:DNA, Viral; D004268:DNA-Binding Proteins; D012367:RNA, Viral; D015678:Viral Structural Proteins; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; C439525:protein p16, bacteriophage phi29