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Following helicase treatment, the single-strand DNA is visually detected as separate from the double-strand DNA by non-denaturing PAGE electrophoresis. Following detection of the single-strand DNA, the amount of radioactive tag that is on the single-strand DNA is quantified to give a numerical value for the amount of double-strand DNA unwinding.
ATP-dependent DNA helicase Q1 is an enzyme that in humans is encoded by the RECQL gene. [5] [6] [7] The protein encoded by this gene is a member of the RecQ DNA helicase family. DNA helicases are enzymes involved in various types of DNA repair, including mismatch repair, nucleotide excision repair and direct repair.
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.
Structurally, DHX36 is a 1008 amino acid-long modular protein that has been crystallized in a complex with a DNA G-quadruplex. [6] It consists of a ~440-amino acid helicase core comprising all signature motifs of the DEAH/RHA family of helicases with N- and C-terminal flanking regions of ~180 and ~380 amino acids, respectively.
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]
RuvA (Holliday junction branch migration complex subunit RuvA) [4] is a DNA-binding protein that binds Holliday junctions with high affinity. The structure of the complex has been variously elucidated through X-ray crystallography and EM data, and suggest that the complex consists of either one or two RuvA tetramers, with charge lined grooves through which the incoming DNA is channelled.
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.
RecBCD is a model enzyme for the use of single molecule fluorescence as an experimental technique used to better understand the function of protein-DNA interactions. [23] The enzyme is also useful in removing linear DNA, either single- or double-stranded, from preparations of circular double-stranded DNA, since it requires a DNA end for activity.