UvrABC endonuclease is a multienzyme complex in
bacteria involved in
DNA repair by
nucleotide excision repair
Nucleotide excision repair is a DNA repair mechanism. DNA damage occurs constantly because of chemicals (e.g. intercalating agents), radiation and other mutagens. Three excision repair pathways exist to repair single stranded DNA damage: Nucle ...
, and it is, therefore, sometimes called an
excinuclease. This UvrABC repair process, sometimes called the short-patch process, involves the removal of twelve nucleotides where a genetic mutation has occurred followed by a DNA polymerase, replacing these aberrant nucleotides with the correct nucleotides and completing the
DNA repair. The subunits for this enzyme are encoded in the ''uvrA'', ''uvrB'', and ''uvrC'' genes. This enzyme complex is able to repair many different types of damage, including
cyclobutyl dimer formation.
Mechanism
# Two UvrA proteins form a dimer and they both have ATPase/GTPase activity.
# The UvrA
dimer
Dimer may refer to:
* Dimer (chemistry), a chemical structure formed from two similar sub-units
** Protein dimer, a protein quaternary structure
** d-dimer
* Dimer model, an item in statistical mechanics, based on ''domino tiling''
* Julius Dimer ( ...
binds with a UvrB dimer and forms a complex that is able to detect
DNA damage
DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA da ...
. The UvrA dimer functions as the unit responsible for the detection of DNA damage, probably through a mechanism of detecting distortions in the
DNA double helix.
# Upon binding of the UvrA
2B
2 complex to a putative damaged site, the DNA wraps around UvrB
# The UvrA dimer leaves and a UvrC protein comes in and binds to the UvrB and, hence, forms a new UvrBC complex.
# UvrC is responsible for
cleaving the nucleotides either side of the DNA damage.
It cleaves a
phosphodiester bond four nucleotides downstream of the DNA damage, and cleaves a
phosphodiester bond eight nucleotides upstream of the DNA damage and creates a twelve nucleotide excised segment.
#
DNA helicase II (sometimes called UvrD) then comes in and removes the excised segment by removing the base pairing. The UvrB still remains in place even though UvrC has disassociated at this stage, as UvrB may be involved to prevent the
reannealing of the excised DNA.
#
DNA polymerase I
DNA polymerase I (or Pol I) is an enzyme that participates in the process of prokaryotic DNA replication. Discovered by Arthur Kornberg in 1956, it was the first known DNA polymerase (and the first known of any kind of polymerase). It was initiall ...
comes in and fills in the correct nucleotides sequence, kicking off UvrB in the process, and the last phosphodiester bond is completed by DNA ligase.
See also
*
DNA repair
*
endonuclease
Endonucleases are enzymes that cleave the phosphodiester bond within a polynucleotide chain. Some, such as deoxyribonuclease I, cut DNA relatively nonspecifically (without regard to sequence), while many, typically called restriction endonucleases ...
*
Nucleotide excision repair
Nucleotide excision repair is a DNA repair mechanism. DNA damage occurs constantly because of chemicals (e.g. intercalating agents), radiation and other mutagens. Three excision repair pathways exist to repair single stranded DNA damage: Nucle ...
*
DNA
References
External links
*
EC 3.1.21
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