Mechanisms for initiating cellular DNA replication
Feb 24, 2017 · During the loading process, the helicase/helicase-loader complex probably still progresses through a 6:6 intermediate that encircles ssDNA (100, 101), and primase can bind to this dodecamer before helicase loader dissociation. However, precisely when certain factors bind to and release another, or how ATP turnover controls the helicase
Get a quote
Frontiers | A Replisome's journey through the bacterial
Genome duplication requires the coordinated activity of a multi-component machine, the replisome. In contrast to the background of metabolic diversity across the bacterial domain, the composition and architecture of the bacterial replisome seem to have suffered few changes during evolution. This immutability underlines the replisome's efficiency in copying the genome.
Get a quote
2018 Bacterial replisomes
at oriC and loading of the DnaB 6–(DnaC) 6 helicase–loader complex onto the DNA bubble. Lower schematic: ATP-bound DnaA binds to DnaA-boxes via Domain IV, thereby promoting dsDNA to wrap around the DnaA filament, causing torsional strain to the dsDNA [8,9]. Meantime, Domain III of DnaA binds to one of the two ssDNA strands of DUE and
Get a quote
Architecture of a Dodecameric Bacterial Replicative Helicase
Hexameric DnaB helicases are often loaded at DNA replication forks by interacting with the initiator protein DnaA and/or a helicase loader (DnaC in Escherichia coli). These loaders are not universally required, and DnaB from Helicobacter pylori was found to bypass DnaC when expressed in E. coli cells. The crystal structure of Helicobacter pylori DnaB C-terminal domain …
Get a quote
Chapter 9: DNA Replication – Chemistry
Subsequent to the remodelling of the replication origin induced by DnaA, the assembly of the bacterial loader-dependent primosome occurs in discrete steps and involves at least four different proteins (initiator protein, helicase, helicase loader protein, and primase) that act in a coordinated and sequential manner (Table 9.1).
Get a quote
'Modulation of the enzymatic activities of replicative
Bacillus subtilis encodes helicase-loader DnaI (18, 19), which cooperates with a co-loader protein DnaB (not to be confused with the EcDnaB helicase) to load the replicative helicase DnaC (not to be confused with the helicase-loader EcDnaC) . In spite of having limited sequence similarity among the helicase loaders (mainly confined to their
Get a quote
Mechanisms in the loading of the replicative DNA helicase
Importantly, the work demonstrated that the MCM2–7 helicase becomes loaded onto DNA as a single hexamer during ORC/Cdc6/Cdt1/MCM2–7 complex formation prior to MCM2–7 double hexamer formation. This study established the existence of a unique DNA entry gate for regulated helicase loading, revealing key mechanisms in helicase loading.
Get a quote
Physical Basis for the Loading of a Bacterial Replicative
Arias-Palomo et al. present the cryo-EM structures of a replicative bacterial helicase-loader complex (E. coli DnaBC) in pre- and post-loading states, revealing how the loader breaks the helicase ring to deposit it at the origin of replication and how ssDNA engagement closes and activates the helicase.
Get a quote
Replication termination mechanism as revealed by Tus
a helicase assay mostly in the standard helicase buffer and in some cases with the same buffer supplemented with 100 mM KCl. It should be noted that in the standard buffer without additional KCl we have reconstituted replication with purified proteins and have observed robust Tus-mediated replication termination in vitro (28).
Get a quote25.1: DNA Replication - Biology LibreTexts
Aug 10, 2021 · Figure 25.1.5 Assembly of a Primosome. DNA melting at oriC and loading of the DnaB 6 –(DnaC) 6 helicase–loader complex onto the DNA bubble. Lower schematic: ATP-bound DnaA (the initiator protein) binds to DnaA-boxes via Domain IV, thereby promoting dsDNA to wrap around the DnaA filament, causing torsional strain to the dsDNA.
Get a quote
How a DNA polymerase clamp loader opens a sliding clamp.
Figure 6. A detailed mechanism for the clamp loading reaction. The reaction cycle for the T4 clamp loader is shown as a schematic diagram. (1) In the absence of ATP, the clamp loader AAA+ modules cannot organize into a spiral shape. (2) Upon ATP binding, the AAA+ modules form a spiral that can bind and open the clamp.
Get a quote
Physical Basis for the Loading of a Bacterial Replicative
Feb 20, 2019 · In cells, dedicated AAA+ ATPases deposit hexameric, ring-shaped helicases onto DNA to initiate chromosomal replication. To better understand the mechanisms by which helicase loading can occur, we used cryo-EM to determine sub-4 Å-resolution structures of the E. coli DnaB•DnaC helicase•loader complex with nucleotide in pre- and post-DNA engagement states.
Get a quote
Lessons Learned from UvrD Helicase: Mechanism for
How do molecular motors convert chemical energy to mechanical work? Helicases and nucleic acids offer simple motor systems for extensive biochemical and biophysical analyses. Atomic resolution structures of UvrD-like helicases complexed with DNA in the presence of AMPPNP, ADP·Pi, and Pi reveal several salient points that aid our understanding of mechanochemical …
Get a quote
Structure and primase-mediated activation of a bacterial
Transition from a loaded helicase•helicase-loaders•primase complex to an active unwinding primosome requires additional conformational changes of the helicase. Closing of the helicase rings is likely facilitated by nucleotide and ssDNA binding since the translocation conformation of DnaB on ssDNA is also spiral ( 12 ).
Get a quote
Viral hijacking of a replicative helicase loader and its
May 31, 2016 · Cells must copy their DNA in order to grow and divide. DNA replication begins when a small region of the DNA double helix is unwound to expose single strands of DNA. A protein called a helicase is then shepherded …
Get a quote
A structural view of bacterial DNA replication - Oakley
Apr 04, 2019 · As noted above, helicases are sometimes loaded onto ssDNA by helicase loader proteins. Helicase loaders are members of the AAA+ (ATPases associated with various cellular activities) superfamily of nucleotide hydrolases. In E. coli, helicase loader DnaC is believed to act as a "ring-breaker," parting a subunit interface in the DnaB helicase
Get a quote
The initiator protein DnaA, chromosomal origin oriC and
of helicase protein by helicase loader leads to melting of the duplex DNA and sets a platform for chromosome replication5,6. Formation of nucleoprotein complexes at the Escherchia coli chro-mosomal origin (oriC) is mediated by DnaA, an initiator protein7–9, which is suggested to be a homologue of S. cerevisiae, Orc1/cdc6 protein10. DnaA
Get a quote
Viral hijacking of a replicative helicase loader and its
May 31, 2016 · (B) Schematic summarizing the auto-regulation of DnaC/I helicase loaders and the ability of phage 77-family viruses to inhibit host helicase loading and co-opt host replicative helicases in S. aureus and related Gram-positive bacteria. The bacterial helicase loader linker region forms an intra-molecular interaction with its associated AAA+
Get a quote
Physical Basis for the Loading of a Bacterial Replicative
Apr 04, 2019 · In cells, dedicated AAA+ ATPases deposit hexameric, ring-shaped helicases onto DNA to initiate chromosomal replication. To better understand the mechanisms by which helicase loading can occur, we used cryo-EM to determine sub-4-Å-resolution structures of the E. coli DnaB⋅DnaC helicase⋅loader complex with nucleotide in pre- and post-DNA engagement states.
Get a quote
Bacterial initiators form dynamic filaments on single
Jan 09, 2015 · These highly coordinated helicase loading mechanisms require a well-coordinated DnaA assembly. In the presence of ATP, E. coli DnaA shows a preference for binding to the T-rich instead of the A-rich strand in the DUE, potentially an indication that DnaA has a preferential binding directionality 3′ to 5′ ( 9, 17, 20 ).
Get a quote