Regulation of histidase synthesis in intergeneric hybrids of enteric bacteria

Abstract

Regulation of the expression of the histidase coded by hutK of Klebsiella aerogenes in Salmonella typhimurium and in Escherichia coli and of the expression of the histidase coded by huts of S. typhimurium in E. coli was investigated. The hutK histidase was found to be sensitive to catabolite repression in K. aerogenes and in E. coli, but insensitive to catabolite repression in S. typhimurium; huts histidase has previously been shown to be catabolite sensitive in all three organisms. The expression of both hutK and huts histidase in E. coli was activated by nitrogen starvation. Apparently, the glutamine synthetase ofE. coli may activate the formation of some glutamate-and ammonia-producing enzymes. Salmonella typhimurium and Klebsiella aerogenes are able to degrade histidine to glutamate, ammonia, and formamide; in both organisms the structural genes for the first two enzymes of the pathway, histidase (EC 4.3.13) and urocanase (EC 4.2.1.49), are in one hut operon, and the structural genes for the third and fourth enzymes of the pathway, imidazolonepropionase (EC 3.5.2.9) and formiminoglutamase (EC 3.5.3.8), are in the second, closely linked hut operon (7, 9, 17). Neidhardt and Magasanik observed that in K. aerogenes the formation of histidase was subject to strong catabolite repression when the organism was grown in a medium containing glucose, histidine, and ammonium sulfate (11); they observed little repression of histidase when the cells were grown in a medium containing glucose and histidine but no ammonium salt. This observation has recently been

gltB gene and regulation of nitrogen metabolism by glutamine synthetase in Escherichia coli

“…Various studies have shown that the GS of E. coli is capable of regulating the synthesis of nitrogen-utiliing enzymes when in the cytoplasm of K. aerogenes, and that the hut operons from both S. typhimurium and K. aerogenes are regulated by GS when transferred into E. coli (7,14,30). It would seem, therefore, that the GS of E. coli possesses the ability to regulate gene expression and that E. coli has all of the necessary components for the regulation of native genes.…”

“…Previous work has established that the glutamine synthetase (EC 6.3.1.2) of Escherichia coli (GS5) can regulate the expression ofgenes native to KiebsieUa aerogenes (14,30). When the structural gene for glutine synthetase (glnA region) of E. coli is tansfenred into a strain of K. aerogenes lacking GS, the GSE has regulatory properties similar to that of the native GSK (30).…”

Transcriptional repression of gdhA in Escherichia coli is mediated by the Nac protein

“…In contrast, the K. aerogenes hutC gene is only slightly regulated by nitrogen conditions in E. coli [6]. In addition, there are con£icting reports regarding GDH regulation by N-availability [2,7^11], making it di¤cult to conclude if histidase and GDH are regulated in E. coli.…”

Regulation of derepressed synthesis of arylsulfatase by tyramine oxidase in Salmonella typhimurium

“…Relief of ammonium repression. It is known that ammonium ions repress the syntheses of some nitrogen-dissimilating enzymes in E. coli (19), S. typhimurium (5), and K. aerogenes (5,19) when the cells are grown in glucose medium, and that this repression is relieved when the cells are grown with a poor nitrogen source. Catabolite repression of tyramine oxidase by glucose in K. aerogenes was relieved when tyramine was used as a nitrogen source, even in the presence of glucose (15,16).…”