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1976 – Discovery and isolation of E. coli-based DNA helicase [13] 1978 – Discovery of the first eukaryotic DNA helicases, isolated from the lily plant [14] 1982 – "T4 gene 41 protein" is the first reported bacteriophage DNA helicase [15] 1985 – First mammalian DNA helicases isolated from calf thymus [17]
During DNA replication, the double helix is unwound and the complementary strands are separated by the enzyme DNA helicase, creating what is known as the DNA replication fork. Following this fork, DNA primase and DNA polymerase begin to act in order to create a new complementary strand.
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.
Bind to ssDNA and prevent the DNA double helix from re-annealing after DNA helicase unwinds it, thus maintaining the strand separation, and facilitating the synthesis of the new strand. Topoisomerase: Relaxes the DNA from its super-coiled nature. DNA gyrase: Relieves strain of unwinding by DNA helicase; this is a specific type of topoisomerase ...
Chromodomain-helicase-DNA-binding protein 1-like (ALC1) is an enzyme that in humans is encoded by the CHD1L gene. [5] [6] It has been implicated in chromatin remodeling and DNA relaxation process required for DNA replication, repair and transcription. The ALC1 comprises ATPase domain and macro domain.
The enzyme has both primase and polymerase functions in addition to helicase function. The gene coding for it is found in a prophage. [17] It bears homology to ORF904 of plasmid pRN1 from Sulfolobus islandicus, which has an AEP PrimPol domain. [23] Vaccinia virus D5 and HSV Primase are examples of AEP-helicase fusion as well. [12] [6]
DNA gyrase, or simply gyrase, is an enzyme within the class of topoisomerase and is a subclass of Type II topoisomerases [1] that reduces topological strain in an ATP dependent manner while double-stranded DNA is being unwound by elongating RNA-polymerase [2] or by helicase in front of the progressing replication fork.