DNA ligase

from Wikipedia, the free encyclopedia
DNA ligase
DNA ligase
ATP-dependent DNA ligase with DNA to be ligated.
Identifier
External IDs
Enzyme classification
EC, category 6.5.1. ,  Ligase
Substrate (Deoxyribonucleotide) m + (deoxyribonucleotide) n
Products (Deoxyribonucleotide) m + n

DNA ligases are enzymes that connect strands of DNA . They form an ester bond between a phosphate residue and the sugar deoxyribose. They belong to the ligases in the EC number nomenclature and have the number EC 6.5.1.- .  

Cut nucleic acids are produced during various processes within cells:

  • During DNA replication , discontinuous pieces of DNA, the Okazaki fragments, are created on the discontinuous strand . The connection of these pieces is accomplished by ligases.
  • Ligases repair strand breaks in various DNA repair mechanisms.
    The DNA ligase links the 5'-phosphate of one strand to the 3'-OH of the other strand.

use

The ligases isolated or recombinantly produced from organisms in molecular biology are an indispensable tool, e.g. B. for genetic engineering: In order to reconnect DNA fragments in a targeted manner, the fragments cut using restriction endonucleases are incubated together with the DNA ligase and the corresponding cofactor . The ligase links the DNA strands so that, for example, a circular plasmid is produced again, which can then be transformed into bacterial cells .

The most commonly used DNA ligases are:

  • T4 DNA ligase : It can link both smooth and overhanging restriction ends. This enzyme needs ATP as a cofactor .
  • E. coli DNA ligase: it cannot connect blunt ends and needs overhanging ends. This enzyme needs NAD + as a cofactor.
  • Taq DNA ligase : like E. coli DNA ligase, but thermostable

literature

  • Lehman, IR (1974): DNA ligase: structure, mechanism, and function . In: Science. Vol. 186, No. 4166, pp. 790-797. PMID 4377758

Web links