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RecQ is a family of DNA helicase enzymes that are found in various organisms including bacteria, archaea, and eukaryotes (like humans). These enzymes play important roles in DNA metabolism during DNA replication, recombination, and repair. There are five known RecQ helicase proteins in humans: RecQ1, BLM, WRN, RecQ4, and RecQ5.
As with prokaryotes, two replisomes are required, one at each replication fork located at the terminus of the replication bubble. Because of significant differences in chromosome size, and the associated complexities of highly condensed chromosomes, various aspects of the DNA replication process in eukaryotes, including the terminal phases, are ...
DnaB helicase is an enzyme in bacteria which opens the replication fork during DNA replication.Although the mechanism by which DnaB both couples ATP hydrolysis to translocation along DNA and denatures the duplex is unknown, a change in the quaternary structure of the protein involving dimerisation of the N-terminal domain has been observed and may occur during the enzymatic cycle. [1]
The two polymerases are bound to the helicase hexamer. In eukaryotes the helicase wraps around the leading strand, and in prokaryotes it wraps around the lagging strand. [40] As helicase unwinds DNA at the replication fork, the DNA ahead is forced to rotate. This process results in a build-up of twists in the DNA ahead. [41]
A) Circular bacterial chromosomes contain a cis-acting element, the replicator, that is located at or near replication origins. i) The replicator recruits initiator proteins in a DNA sequence-specific manner, which results in melting of the DNA helix and loading of the replicative helicase onto each of the single DNA strands (ii).
DnaC helps the helicase to bind to and to properly accommodate the ssDNA at the 13 bp region; this is accomplished by ATP hydrolysis, after which DnaC is released. Single-strand binding proteins (SSBs) stabilize the single DNA strands in order to maintain the replication bubble. DnaB is a 5'→3' helicase, so it travels on the lagging strand.
RecQ helicase is a family of helicase enzymes initially found in Escherichia coli [1] that has been shown to be important in genome maintenance. [2] [3] [4] They function through catalyzing the reaction ATP + H 2 O → ADP + P and thus driving the unwinding of paired DNA and translocating in the 3' to 5' direction.
When Mcm2-7 is first loaded it completely encircles the DNA and helicase activity is inhibited. In S phase, the Mcm2-7 complex interacts with helicase cofactors Cdc45 and GINS to isolate a single DNA strand, unwind the origin, and begin replication down the chromosome. In order to have bidirectional replication, this process happens twice at an ...