Methods in Molecular Biology • 16 Enzymes of Molecular Biology

(Nancy Kaufman) #1
CHAPTER 10

DNA and RNA Ligases
(EC 6.5.1.1, EC 6.5.1.2, and EC 6.5.1.3)

Martin J. Maunders



  1. Introduction
    Ligases are a class of enzymes that catalyze the joining of nucleic
    acid molecules by the formation of phosphodiester bonds between
    their termini (1). The nucleic acid substrate to be linked may be DNA
    or RNA depending on the type of ligase involved.
    The enzymes are widespread and have been identified in a range of
    organisms, including bacteria (2, 3), phage-infected bacteria (4), yeasts
    (5), amphibians (6), and mammals (5), including Homo sapiens (7).
    Many ligase-deficient and ligase-overproducing mutants have been
    isolated, and levels of enzyme in the E. coli bacterium can vary 1000-
    fold (from 0.01 to 10 x normal) without deleterious effect.

  2. DNA Ligases (EC 6.5.1.1-2)
    The role of DNA ligases in vivo is believed to include the joining
    of short DNA fragments formed during DNA replication (8), and so
    enabling DNA synthesis to progress in an overall 3'-5' direction on the
    antiparallel strand of the double helix, while continual 5'-3' synthesis
    proceeds on the other strand.
    Other possible functions of DNA ligases include roles during genetic
    recombination and in the repair of UV-damaged DNA (9), though
    ligase- bacterial mutants can in general perform these functions suf-
    ficiently well. In yeast, however, there is evidence to support the idea
    of a role for DNA ligases in UV damage repair (10).


From: Methods in Molecular Biology, Vol. 16: Enzymes of Molecular Biology
Edited by: M. M. Burrell Copyright ©1993 Humana Press Inc., Totowa, NJ

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