The biosynthesis of glutamate lies at the intersection of carbon and nitrogen metabolism, linking the Krebs citric acid cycle to nitrogen assimilation through glutamine synthetase. In Bacillus subtilis, the genes for glutamate synthesis and for the pathways leading to the precursors of glutamate are tightly regulated by a host of proteins that respond to a variety of metabolic signals. The long-term goal of this project is to unravel and understand the network of genes, enzymes, and regulatory proteins that allow the cell to maintain tight control over glutamate accumulation. Building on knowledge gained from previous work, this proposal aims to focus on the roles of two of these regulatory proteins, CcpC and GItC. Two aspects of CcpC function will be investigated: interaction with the inducer, citrate, and the role of multimerization in repression. For GItC, the metabolite or protein that regulates its activity will be identified, in addition, the broad role of GltC in gene regulation and its functional interaction with other regulatory proteins will be explored. One of the Krebs cycle enzymes, aconitase, may have a second, non-enzymatic activity, perhaps as an RNA binding protein. The putative secondary activity of aconitase will be tested by seeking targets of such a function and by creating mutants that retain enzymatic activity but have lost the non-enzymatic activity. The implications of this second activity for sporulation in B. subtilis will receive particular attention. Since B. subtilis is a model organism for the gram-positive branch of the bacterial world, the knowledge gained here will be applied to a related, pathogenic species, Listeria monocytogenes. Thus, this proposal seeks to take advantage of the apparent conservation of regulatory proteins, gene organization and regulatory sites between B. subtilis and L. monocytogenes and thereby make rapid progress in an unexplored aspect of the life of an important pathogen. ? ? ?
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