Michael Cashel

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The fundamental details of how nutritional stress leads to elevating (p)ppGpp are questionable. By common usage, the meaning of the stringent response has evolved from the specific response to (p)ppGpp provoked by amino acid starvation to all responses caused by elevating (p)ppGpp by any means. Different responses have similar as well as dissimilar positive(More)
It was known previously that 1) the relA gene of Escherichia coli encodes an enzyme capable of guanosine 3',5'-bispyrophosphate (ppGpp) synthesis, 2) an uncharacterized source of ppGpp synthesis exists in relA null strains, and 3) cellular degradation of ppGpp is mainly due to a manganese-dependent ppGpp 3'-pyrophosphohydrolase encoded by the spoT gene.(More)
The RpoS sigma factor (also called sigmaS or sigma38) is known to regulate at least 50 genes in response to environmental sources of stress or during entry into stationary phase. Regulation of RpoS abundance and activity is complex, with many factors participating at multiple levels. One factor is the nutritional stress signal ppGpp. The absence of ppGpp(More)
High levels of guanosine tetraphosphate (ppGpp) and guanosine pentaphosphate (pppGpp), generated in response to amino acid starvation in Escherichia coli, lead to massive accumulations of inorganic polyphosphate (polyP). Inasmuch as the activities of the principal enzymes that synthesize and degrade polyP fluctuate only slightly, the polyP accumulation can(More)
Strains of Escherichia coli which lack detectable guanosine 3',5'-bispyrophosphate (ppGpp) display a pleiotropic phenotype that in some respects resembles that of rpoS (katF) mutants. This led us to examine whether ppGpp is a positive regulator of sigma s synthesis. sigma s is a stationary-phase-specific sigma factor that is encoded by the rpoS gene. We(More)
Intracellular levels of guanosine 3',5'-bispyrophosphate (ppGpp) governed by the relA gene are normally regulated by aminoacyl-tRNA availability for protein synthesis. An experimental system is described in which cellular levels of ppGpp are controlled instead by induction of plasmid pKK223-3 derivatives with the relA structural gene, or portions thereof,(More)
Stringent strains of Escherichia coli are shown to produce one, and usually two, 82P-labeled compounds specifically in response to amino acid starvation. This pattern of labeling is not observed in three derived relaxed strains. Comparison of properties of the system regulating the synthesis of these compounds with those of the amino acid control of RNA(More)
The spoT gene of Escherichia coli encodes a guanosine 3',5'-bis(diphosphate) 3'-pyrophosphohydrolase (ppGppase) as well as an apparent guanosine 3',5'-bis(diphosphate) synthetase (designated PSII). To determine the regions of the SpoT protein that are required for these two competing activities, we analysed plasmid-borne deletion mutations for their ability(More)