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J Bacteriol. 2003 Nov;185(22):6732-5.

A mutation in the essential gene gmk (encoding guanlyate kinase) generates a requirement for adenine at low temperature in Salmonella enterica.

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Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.


In Salmonella enterica serovar Typhimurium, gmk encodes guanylate kinase, an essential enzyme involved in the synthesis and salvage of guanine nucleotides. Here we report the isolation of a mutation in gmk that results in a nutritional requirement for adenine at low temperature. Comparisons of kinetic parameters from the wild-type and mutant Gmk enzymes revealed that the mutant enzyme had a more than 20-fold-higher Km for ATP than the wild-type enzyme. The growth dependence of the mutant on temperature and/or adenine could not be explained as a direct result of this kinetic difference. We propose a model in which previously described regulatory effects of GMP are responsible for these phenotypes.

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