DnaB helicase

Overview

DnaB helicase is a protein that plays a crucial role in the process of DNA replication. This enzyme is responsible for unwinding the double-stranded DNA helix, allowing the replication machinery to access the single-stranded DNA templates. DnaB helicase is a highly conserved protein, meaning it is found in many different species, from bacteria to humans.

Structure

DnaB helicase is a hexameric protein, meaning it is composed of six identical subunits. Each subunit is made up of a large N-terminal domain and a smaller C-terminal domain. The N-terminal domain is responsible for ATP hydrolysis, which provides the energy for DNA unwinding. The C-terminal domain is involved in protein-protein interactions, particularly with the DnaG primase.

Function

The primary function of DnaB helicase is to unwind the double-stranded DNA helix during replication. It does this by breaking the hydrogen bonds between the two strands of DNA, effectively separating them. This unwinding process allows the replication machinery, including DNA polymerase and primase, to access the single-stranded DNA templates and begin the process of replication.

DnaB helicase is also involved in the initiation of DNA replication. It interacts with the DnaA protein, which is responsible for recognizing the origin of replication and initiating the replication process. DnaB helicase is then loaded onto the DNA by the DnaC protein, allowing it to begin unwinding the DNA.

Mechanism of Action

DnaB helicase unwinds DNA using a mechanism known as steric exclusion. In this mechanism, the helicase binds to one strand of the DNA and moves along it, displacing the other strand. This displacement of the second strand causes the DNA to unwind.

The unwinding process is powered by ATP hydrolysis, which occurs in the N-terminal domain of the DnaB helicase. The energy released by this hydrolysis is used to break the hydrogen bonds between the DNA strands, allowing them to separate.

Role in Disease

Mutations in the DnaB helicase can lead to problems with DNA replication, which can in turn lead to genetic diseases. For example, mutations in the DnaB helicase have been associated with certain types of cancer, as well as with premature aging syndromes.