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  • Title: Mammalian DNA ligases. Catalytic domain and size of DNA ligase I.
    Author: Tomkinson AE, Lasko DD, Daly G, Lindahl T.
    Journal: J Biol Chem; 1990 Jul 25; 265(21):12611-7. PubMed ID: 1695631.
    Abstract:
    DNA ligase I is the major DNA ligase activity in proliferating mammalian cells. The protein has been purified to apparent homogeneity from calf thymus. It has a monomeric structure and a blocked N-terminal residue. DNA ligase I is a 125-kDa polypeptide as estimated by sodium dodecyl sulfate-gel electrophoresis and by gel chromatography under denaturing conditions, whereas hydrodynamic measurements indicate that the enzyme is an asymmetric 98-kDa protein. Immunoblotting with rabbit polyclonal antibodies to the enzyme revealed a single polypeptide of 125 kDa in freshly prepared crude cell extracts of calf thymus. Limited digestion of the purified DNA ligase I with several reagent proteolytic enzymes generated a relatively protease-resistant 85-kDa fragment. This domain retained full catalytic activity. Similar results were obtained with partially purified human DNA ligase I. The active large fragment represents the C-terminal part of the intact protein, and contains an epitope conserved between mammalian DNA ligase I and yeast and vaccinia virus DNA ligases. The function of the N-terminal region of DNA ligase I is unknown.
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