In Escherichia coli -- and likely other bacteria -- high-energy intermediates of central metabolism [e.g. acetyl phosphate (acP) and acetyl-coenzyme A (acCoA)] appear to control global gene expression -- at least in part - through a subset of signaling proteins called two-component signal transduction (2CST) response regulators (RRs). The high-energy status of acP and acCoA makes each an excellent donor: acP can donate its phosphoryl group, while acCoA can donate its acetyl group. Coupled with their central position in metabolism, these abilities make acP and acCoA ideally suited to indicate nutritional status and thereby impact a variety of cellular processes. This proposal will test key aspects of the following hypothesis. Cells exposed to excess carbon experience a central metabolic stress associated with their inability to recycle coenzymeA (CoA) rapidly enough. Because CoA is present in limiting amounts, the acCoA:CoA ratio becomes large. To recycle the metabolically essential CoA, some of the excess acetyl groups pass from CoA to inorganic phosphate. This process results in the synthesis of acP, which has been proposed to donate its phosphoryl group to a subset of 2CSTRRs. Alternatively or simultaneously, other acetyl groups can be donated directly to a second subset of RRs, thereby altering their function. This hypothesis is broadly based on the following observations: (i) cells manipulate the ratio of acCoA and acP during growth and in response to the quality and quantity of carbon source. (ii) cells respond globally to variations in the concentrations of both high-energy central metabolites;(iii) the response to acP depends on the action of at least one RR and likely more;(iv) two promoters, each dependent on a different RR, appear to respond to the status of the acCoA pool;and (v) acCoA has been shown to donate its acetyl group to 2 purified RRs. 2CST pathways regulate diverse processes associated with biofilm development and pathogenesis. Because humans do not express 2CST pathways, the abilities of acP and acCoA to modify RRs represent a prime target for anti-microbial strategies.
This proposal will test the hypothesis that acetyl coenzyme A and acetyl phosphate, high-energy intermediates of central metabolism, can modify - by acetylation or phosphorylation, respectively - and thereby alter the function of signaling proteins that contribute to biofilm development by and virulence of diverse pathogens. Because humans do not express these signaling proteins, called response regulators, these interactions represent a prime target for anti-microbial strategies.
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