title: The replication initiator protein pi of the plasmid R6K specifically interacts with the host-encoded helicase DnaB.
abstract: The replication initiator protein pi of plasmid R6K is known to interact with the seven iterons of the gamma origin/enhancer and activate distant replication origins alpha and beta (ori alpha and ori beta) by pi-mediated DNA looping. Here we show that pi protein specifically interacts in vitro with the host-encoded helicase DnaB. The site of interaction of pi on DnaB has been localized to a 37-aa-long region located between amino acids 151 and 189 of DnaB. The surface of pi that interacts with DnaB has been mapped to the N-terminal region of the initiator protein between residues 1 and 116. The results suggest that during initiation of replication, the replicative helicase DnaB is first recruited to the gamma enhancer by the pi protein. In a subsequent step, the helicase probably gets delivered from ori gamma to ori alpha and ori beta by pi-mediated DNA looping.
authors.affiliation: Department of Microbiology, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: P V
authors.initials: PV
authors.lastname: Ratnakar
authors.forename: B K
authors.initials: BK
authors.lastname: Mohanty
authors.forename: M
authors.initials: M
authors.lastname: Lobert
authors.forename: D
authors.initials: D
authors.lastname: Bastia
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D001665:Binding Sites; D004265:DNA Helicases / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D004261:DNA Replication; D004268:DNA-Binding Proteins; D053488:DnaB Helicases; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D005982:Glutathione Transferase / Q000096:biosynthesis; D007700:Kinetics; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D014176:Protein Biosynthesis; D011815:R Factors; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000302:isolation & purification; D015534:Trans-Activators / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; C045264:replication initiator protein; D005982:Glutathione Transferase; D004265:DNA Helicases; D053488:DnaB Helicases