Characterization of regulatory mutations affecting thekbl/tdh operon of Escherichia coli
Abstract
The enzymes encoded by the kbl/tdh operon of Escherichia coli catalyze sequential steps in the conversion of threonine to glycine. These enzymes, threonine dehydrogenase and 2-amino-3-ketobutyrate coenzyme A ligase, are normally expressed at low levels in the cell, the majority of glycine being synthesized from serine via the action of the glyA gene product, serine hydroxymethyl-transferase. In order to gain further understanding of physiological role of the kbl/tdh operon, its expression during growth and in response to certain inducers was studied. In addition, mutations allowing a glyA mutant to grow in the absence of glycine were isolated. Two of the mutations isolated and characterized yielded a significant increase on kbl/tdh operon expression. These mutations are in the genes for hns and cya. The regulation of the kbl/tdh operon by these proteins and its interaction with the leucine responsive regulatory protein (Lrp), another known regulator of this operon, lend support to the hypothesis that the enzymes encoded by the kbl/tdh operon function during adaptation to stress or major changes in environment such as those that occur when the cell leaves the mammalian gut.
Degree
Ph.D.
Advisors
Levinthal, Purdue University.
Subject Area
Microbiology|Genetics
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