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DNA ligase is a type of enzyme that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond.It plays a role in repairing single-strand breaks in duplex DNA in living organisms, but some forms (such as DNA ligase IV) may specifically repair double-strand breaks (i.e. a break in both complementary strands of DNA).
T4 DNA ligase used to cyclize short ssDNA fragments, but process is complicated by formation of secondary structures. On the other hand, Taq DNA ligase is a thermostable enzyme which can be applied at higher temperatures (45, 55 and 65 °C respectively). Since at these temperature range secondary structures less stable it is enhance cyclization ...
For example, DNA ligase can join two complementary fragments of nucleic acid by forming phosphodiester bonds, and repair single stranded breaks that arise in double stranded DNA during replication. In general, a ligase catalyzes the following dehydration reaction, thus joining molecules A and B: A-OH + B-H → A–B + H 2 O
In NHEJ, DNA Ligase IV, a specialized DNA ligase that forms a complex with the cofactor XRCC4, directly joins the two ends. [25] To guide accurate repair, NHEJ relies on short homologous sequences called microhomologies present on the single-stranded tails of the DNA ends to be joined. If these overhangs are compatible, repair is usually accurate.
DNA ligase 1 also DNA ligase I, is an enzyme that in humans is encoded by the LIG1 gene. DNA ligase 1 is the only known eukaryotic DNA ligase involved in both DNA replication and repair , making it the most studied of the ligases .
The alternative translation initiation and splicing mechanisms alter the amino- and carboxy-terminal sequences that flank the DNA ligase III catalytic region. [15] [16] In the alternative splicing mechanism, the exon encoding a C-terminal breast cancer susceptibility protein 1 C-terminal domain at the C-terminus of DNA ligase III-alpha is replaced by a short positively charged sequence that ...
DNA ligase is an enzyme that joins together ends of DNA molecules. Although commonly represented as joining two pairs of ends at once, as in the ligation of restriction enzyme fragments, ligase can also join the ends on only one of the two strands (for example, when the other strand is already continuous or lacks a terminal phosphate necessary for ligation).
Recognition of the damage leads to removal of a short single-stranded DNA segment that contains the lesion. The undamaged single-stranded DNA remains and DNA polymerase uses it as a template to synthesize a short complementary sequence. Final ligation to complete NER and form a double stranded DNA is carried out by DNA ligase. NER can be ...