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There are two main types of primase: DnaG found in most bacteria, and the AEP (Archaeo-Eukaryote Primase) superfamily found in archaean and eukaryotic primases. While bacterial primases (DnaG-type) are composed of a single protein unit (a monomer) and synthesize RNA primers, AEP primases are usually composed of two different primase units (a heterodimer) and synthesize two-part primers with ...
The E. Coli DnaG primase is a 581 residue monomeric protein with three functional domains, according to proteolysis studies. There is an N-terminal Zinc-binding domain (residues 1–110) where a zinc ion is tetrahedrally coordinated between one histidine and three cysteine residues, which plays a role in recognizing sequence specific DNA binding sites.
DNA polymerase alpha, like DNA primase, contains iron-sulfur clusters, that are critical in electron transport that uses DNA itself to transfer electrons at very high speeds; this process is involved in detecting DNA damage, and may also be involved in a feedback between the primase complex and the DNA polymerase alpha.
This gene encodes the p180 catalytic subunit of DNA polymerase α-primase. Pol α has limited processivity and lacks 3′ exonuclease activity for proofreading errors. Thus it is not well suited to efficiently and accurately copy long templates (unlike Pol Delta and Epsilon). Instead it plays a more limited role in replication.
DNA primase small subunit is an enzyme that in humans is encoded by the PRIM1 gene. [ 5 ] The replication of DNA in eukaryotic cells is carried out by a complex chromosomal replication apparatus, in which DNA polymerase alpha and primase are two key enzymatic components.
PrimPol was identified in a bioinformatic study and initially presumed to only have primase activity. [8] Subsequent in vitro and in vivo studies have shown it to have both primase and polymerase activities that both localise to the catalytic domain of PrimPol. [6] [7] [9] For that reason, this protein was assigned the name PrimPol.
Along the DNA template, primase intersperses RNA primers that DNA polymerase uses to synthesize DNA from in the 5′→3′ direction. [1] Another example of primers being used to enable DNA synthesis is reverse transcription. Reverse transcriptase is an enzyme that uses a template strand of RNA to synthesize a complementary strand of DNA.
A helicase–primase complex (also helicase-primase, Hel/Prim, H-P or H/P) is a complex of enzymes including DNA helicase and DNA primase. A helicase-primase associated factor protein may also be present. [1] The complex is used by herpesviruses, in which it is responsible for lytic DNA virus replication.