Involvement of the stringent response in degradation of glutamine phosphoribosylpyrophosphate amidotransferase in Bacillus subtilis

Abstract

Glutamine phosphoribosylpyrophosphate amidotransferase, the first enzyme of purine biosynthesis, has previously been shown to be rapidly inactivated and degraded in Bacillus subtilis cells at the end of growth. The loss of enzyme activity appears to involve the oxidation of an iron-sulfur cluster in the enzyme. The degradation of the inactive enzyme involves some elements of the stringent response because it is inhibited in relA and relC mutants. Intracellular pools of guanosine tetra- and pentaphosphate were measured by an improved extraction procedure in cells that had been manipulated in various ways to induce or inhibit amidotransferase degradation. The results are consistent with the hypothesis that one or both of these nucleotides stimulates the synthesis of a protein involved in degradation. An elevated level of these nucleotides was not required for the continued degradation of amidotransferase once it had begun.

Nucleotide metabolism and its control in lactic acid bacteria

“…The inactivation may be controlled over a wide range by changing the AMP/GMP ratio because AMP stabilizes the enzyme while GMP destabilizes it [76]. Furthermore it has been shown that PurF is stabilized in a relA mutant, suggesting that (p)ppGpp is somehow involved in its degradation [77].…”

General stress proteins in Bacillus subtilis

“…However, information on the fzzn,°ticn ,~f ppGpp in B. subti/,is is rather limited, ppGpp is involved in the control of ribosome synthesis [46] and DNA synthesis [47] similar to E. coli. Furthermore, there are some results on the influence 205 of ppGpp on different physiological reactions in Bacillus (stability of enzymes [48], inhibition of the inosine monophosphate dehydrogenase activity [45]).…”

Degradation of aspartate transcarbamylase in Bacillus subtilis is deficient in rel mutants but is not mediated by guanosine polyphosphates

“…Evidence has been presented that the stringent response, specifically the intracellular level of the nucleotide 3'-pyrophosphorylguanosine-5'-pyrophosphate (ppGpp), regulates the rate of bulk protein degradation in starving Escherichia coli (12,15). Ruppen and Switzer (8,9) have also presented evidence for involvement of the stringent response in regulating intracellular degradation of glutamine phosphoribosylpyrophosphate amidotransferase in B. subtilis. Accordingly, we have examined the rate of ATCase degradation under several nutritional conditions in Rel+ and Rel-strains of B. subtilis.…”

“…We attempted to answer this question by determining the intracellular levels of these nucleotides in each of the strains under each of the culture conditions listed in Tables 1 and 2. The nucleotides were measured by labeling the cultures with 32pi, extraction with 3 M formic acid, and two-dimensional thin-layer chromatography (9). Greater sensitivity was obtained by increasing the amount of formic acid extract analyzed to six times that used by Ruppen and Switzer (9).…”

“…The nucleotides were measured by labeling the cultures with 32pi, extraction with 3 M formic acid, and two-dimensional thin-layer chromatography (9). Greater sensitivity was obtained by increasing the amount of formic acid extract analyzed to six times that used by Ruppen and Switzer (9). During exponential growth, the levels of ppGpp and pppGpp in B. subtilis were quite low; they were lower in cells grown with amino acids than in cells grown with NH4Cl as the nitrogen source ( Table 1).…”