Enzymatic Characterization of a Mutant of Escherichia coli with an Altered DNA Ligase

Abstract
A temperature-sensitive, radiation-sensitive mutant of Escherichia coli has been assayed for DNA ligase activity in vitro. The strain contains a markedly reduced amount of DNA-joining activity, which is thermolabile. The formation of the ligase-adenylate intermediate is also temperature-sensitive in vitro. Two temperature-resistant revertants of the mutant contain normal amounts of a thermostable ligase. The mutant is killed by growth at 42 degrees C, a temperature at which it displays aberrant DNA synthesis. These results suggest that the ligase is necessary for normal DNA metabolism and viability in this strain.

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