title: DnaC traps DnaB as an open ring and remodels the domain that binds primase.
abstract: Helicase loading at a DNA replication origin often requires the dynamic interactions between the DNA helicase and an accessory protein. In E. coli, the DNA helicase is DnaB and DnaC is its loading partner. We used the method of hydrogen/deuterium exchange mass spectrometry to address the importance of DnaB-DnaC complex formation as a prerequisite for helicase loading. Our results show that the DnaB ring opens and closes, and that specific amino acids near the N-terminus of DnaC interact with a site in DnaB's C-terminal domain to trap it as an open ring. This event correlates with conformational changes of the RecA fold of DnaB that is involved in nucleotide binding, and of the AAA+ domain of DnaC. DnaC also causes an alteration of the helical hairpins in the N-terminal domain of DnaB, presumably occluding this region from interacting with primase. Hence, DnaC controls the access of DnaB by primase.
authors.affiliation: Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824-1319, USA.
authors.forename: Sundari
authors.initials: S
authors.lastname: Chodavarapu
authors.affiliation: Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824-1319, USA Department of Chemistry, Michigan State University, East Lansing, MI 48824-1319, USA.
authors.forename: A Daniel
authors.initials: AD
authors.lastname: Jones
authors.affiliation: Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824-1319, USA Department of Chemistry, Michigan State University, East Lansing, MI 48824-1319, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Feig
authors.affiliation: Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824-1319, USA kaguni@msu.edu.
authors.forename: Jon M
authors.initials: JM
authors.lastname: Kaguni
mesh_terms: D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D019915:DNA Primase / Q000378:metabolism*; D053488:DnaB Helicases / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D017433:Protein Structure, Secondary
chemical_list: D001426:Bacterial Proteins; D010455:Peptides; D019915:DNA Primase; D053488:DnaB Helicases