Topic
DnaB-DnaC complex
About: DnaB-DnaC complex is a research topic. Over the lifetime, 2 publications have been published within this topic receiving 75 citations.
Papers
TL;DR: Analysis of the volume brings insight into the elaborate way the two proteins interact, and provides a structural basis for control of the symmetry state and inactivation of the helicase by DnaC, and proposes that the DnaB N‐terminal domain is located at this face.
Abstract: Replicative helicases are motor proteins that unwind DNA at replication forks. Escherichia coli DnaB is the best characterized member of this family of enzymes. We present the 26 A resolution three-dimensional structure of the DnaB hexamer in complex with its loading partner, DnaC, obtained from cryo-electron microscopy. Analysis of the volume brings insight into the elaborate way the two proteins interact, and provides a structural basis for control of the symmetry state and inactivation of the helicase by DnaC. The complex is arranged on the basis of interactions among DnaC and DnaB dimers. DnaC monomers are observed for the first time to arrange as three dumb-bell-shaped dimers that interlock into one of the faces of the helicase. This could be responsible for the freezing of DnaB in a C3 architecture by its loading partner. The central channel of the helicase is almost occluded near the end opposite to DnaC, such that even single-stranded DNA could not pass through. We propose that the DnaB N-terminal domain is located at this face.
80 citations
TL;DR: The reconstructed 3D volume of the DnaB hexamer obtained from frozen-hydrated specimens showed the DnB oligomer as a particle possessing three-fold rather than six-fold symmetry, despite DnaBs being made up by six identical subunits.
Abstract: Strand separation in double stranded DNA is achieved in vivo by a class of enzymes called helicases in a process fuelled by hydrolysis of nucleoside triphosphates. DnaB is the major replicative helicase in E.coli. For chromosomal replication to initiate, DnaB needs to interact with a partner protein, namely DnaC, which after properly loading DnaB onto the DNA template at the origin of replication is subsequently released from the complex. DnaB turns to be functionally active as a helicase only after DnaC has been released from the complex. The native DnaB is a homohexamer of molecular weight 318 kD. In the presence of ATP and Mg2+, the hexameric DnaB has been shown to form a complex with six molecules of DnaC (total molecular weight of the complex: 480 kD). The reconstructed 3D volume of the DnaB hexamer obtained from frozen-hydrated specimens showed the DnaB oligomer as a particle possessing three-fold rather than six-fold symmetry, despite DnaB being made up by six identical subunits.
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2001 | 1 |
| 2000 | 1 |