Each of the four types of
mammalian DNA ligase has a common core structure. The common motif
found in the active site of the enzyme is:
Lys-Tyr/Ala-Asp-Gly-(Xaa)-Arg. The reactive lysine residue that reacts
to form the ligase-adenylate intermediate is neighboring two
hydrophobic amino acids.
While there are common amino acid residues found in the active sites of the mammalian DNA ligase forms, each contain unique end components of their structures that ultimately lead to the distinct pathways in which the enzymes participate. Below is an illustration of DNA ligases I and III, indicating the identical active sites with the reactive lysine residue as well as the varying end structure sequences that aid in directing the enzyme to enter the right DNA repair pathway. The zinc finger of DNA ligase III (which allows the enzyme to quickly locate repair sites) is also illustrated.
This illustration was obtained from the internet (google image search)
The
following picture shows DNA ligase I interacting with a nick in the
double-stranded DNA. DNA ligase I is known to completely encircle the
DNA before forming a phosphodiester bond to seal the nick. The bottom
right of the depiction identifies the active site residues that are
interacting with the DNA at the repair site.
This illustration was obtained from the internet (google image search)
Information for this page was obtained from:
Pascal, John, et al. “Human DNA ligase I completely encircles and partially unwinds nicked DNA.” Nature. 25 November 2004. Nature Publishing Group. 273-278. Accessed from Nature Network <http://www.nature.com/nature/journal/v432/n7016/full/nature03082.html>.
Tomkinson, A.E., et al. “Location of the Active Site for Enzyme-Adenylate Formation in DNA Ligase.” Proc National Academy Science USA. 15 January 1991: Vol 88(2). 400–404. Accessed from PubMed <http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=50818>.
While there are common amino acid residues found in the active sites of the mammalian DNA ligase forms, each contain unique end components of their structures that ultimately lead to the distinct pathways in which the enzymes participate. Below is an illustration of DNA ligases I and III, indicating the identical active sites with the reactive lysine residue as well as the varying end structure sequences that aid in directing the enzyme to enter the right DNA repair pathway. The zinc finger of DNA ligase III (which allows the enzyme to quickly locate repair sites) is also illustrated.
This illustration was obtained from the internet (google image search)
This illustration was obtained from the internet (google image search)
Information for this page was obtained from:
Pascal, John, et al. “Human DNA ligase I completely encircles and partially unwinds nicked DNA.” Nature. 25 November 2004. Nature Publishing Group. 273-278. Accessed from Nature Network <http://www.nature.com/nature/journal/v432/n7016/full/nature03082.html>.
Tomkinson, A.E., et al. “Location of the Active Site for Enzyme-Adenylate Formation in DNA Ligase.” Proc National Academy Science USA. 15 January 1991: Vol 88(2). 400–404. Accessed from PubMed <http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=50818>.
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