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J. Virol., 03 1997, 1931-1937, Vol 71, No. 3
CK Ho, JL Van Etten and S Shuman
We report that Chlorella virus PBCV-1 encodes a 298-amino-acid ATP-
dependent DNA ligase. The PBCV-1 enzyme is the smallest member of the
covalent nucleotidyl transferase superfamily, which includes the ATP-
dependent polynucleotide ligases and the GTP-dependent RNA capping enzymes.
The specificity of PBCV-1 DNA ligase was investigated by using purified
recombinant protein. The enzyme catalyzed efficient strand joining on a
singly nicked DNA in the presence of magnesium and ATP (Km, 75 microM).
Other nucleoside triphosphates or deoxynucleoside triphosphates could not
substitute for ATP. PBCV-1 ligase was unable to ligate across a
2-nucleotide gap and ligated poorly across a 1- nucleotide gap. A native
gel mobility shift assay showed that PBCV-1 DNA ligase discriminated
between nicked and gapped DNAs at the substrate-binding step. These
findings underscore the importance of a properly positioned 3' OH acceptor
terminus in substrate recognition and reaction chemistry.
Copyright © 1997, American Society for Microbiology
Characterization of an ATP-dependent DNA ligase encoded by Chlorella virus PBCV-1
Molecular Biology Program, Sloan-Kettering Institute, New York, New York 10021, USA.
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