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| Keywords: DNA Repair.jpg DNA damage due to environmental factors and normal metabolic processes inside the cell occurs at a rate of 1 000 to 1 000 000 molecular lesions per cell per day A special enzyme DNA ligase shown here in color encircles the double helix to repair a broken strand of DNA DNA ligase is responsible for repairing the millions of DNA breaks generated during the normal course of a cell's life Without molecules that can mend such breaks cells can malfunction die or become cancerous DNA ligases catalyse the crucial step of joining breaks in duplex DNA during DNA repair replication and recombination and require either Adenosine triphosphate ATP or Nicotinamide adenine dinucleotide NAD+ as a cofactor Shown here is DNA ligase I repairing chromosomal damage The three visable protein structures are The DNA binding domain DBD which is bound to the DNA minor groove both upstream and downstream of the damaged area The OB-fold domain OBD unwinds the DNA slightly over a span of six base pairs and is generally involved in nucleic acid binding The Adenylation domain AdD contains enzymatically active residues that join the broken nucleotides together by catalyzing the formation of a phosphodiester bond between a phosphate and hydroxyl group It is likely that all mammalian DNA ligases Ligases I III and IV have a similar ring-shaped architecture and are able to recognize DNA in a similar manner See http //www fhcrc org/science/labs/stoddard/MCB_542/pascal_etal_2004_ligaseI pdf Nature Article 2004 PDF URL http //publications nigms nih gov/biobeat/gallery/RepairingDNA htm Biomedical Beat Cool Image Gallery 2006-11-21 Tom Ellenberger Washington University School of Medicine in St Louis The material in this newsletter is not copyrighted and we encourage its use or reprinting URL https //web archive org/web/20061001183925/http //www nigms nih gov/Publications/Biobeat/ National Institute of General Medical Science PD-USGov LicenseReview URL http //publications nigms nih gov/biobeat/gallery/RepairingDNA htm Biomedical Beat Cool Image Gallery Green Giant 2015-10-08 DNA repair DNA-protein interactions | ||||
