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Journal of Bacteriology, November 2003, p. 6732-6735, Vol. 185, No. 22
0021-9193/03/$08.00+0     DOI: 10.1128/JB.185.22.6732-6735.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

A Mutation in the Essential Gene gmk (Encoding Guanlyate Kinase) Generates a Requirement for Adenine at Low Temperature in Salmonella enterica

Brian J. Beck, Mike Huelsmeyer, Scott Paul, and D. M. Downs^*

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

Received 28 July 2003/ Accepted 28 August 2003

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 K_m 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.

Present address: Department of Medicinal Chemistry, University of Michigan, Ann Arbor, MI 48109-1065.