Mutations affecting catabolite repression of the L-arabinose regulon in Escherichia coli B/r

Abstract

Expression of the L-arabinose regulon in Escherichia coli B/r requires, among other things, cyclic adenosine-3',5'-monophosphate (cAMP) and the cAMP receptor protein (CRP). Mutants deficient in adenyl cyclase (cya-), the enzyme which synthesizes cAMP, or CRP (crp-) are unable to utilize a variety of carbohydrates, including L-arabinose. Ara+ revertants of a cya-crp-strain were isolated on 0.2% minimal L-arabinose plates, conditions which require the entire ara regulon to be activated in the absence of cAMP and CRP. Evidence from genetic and physiological studies is consistent with placing these mutations in the araC regulatory gene. Deletion mapping with one mutant localized the site within either araO or araC, and complementation tests indicated the mutants acted trans to confer the ability to utilize L-arabinose in a cyacrp-genetic background. Since genetic analysis supports the conclusion that the mutant sites are in the araC regulatory gene, the mutants were designated araCi, indicating a mutation in the regulatory gene affecting the cAMP-CRP requirement. Physiological analysis of one mutant, araC'1, illustrates the transacting nature of the mutation. In a cya-crpgenetic background, araC1l promoted synthesis of both isomerase, a product of the araBAD operon, and permease, a product of the araE operon. Isomerase and permease levels in araCi1 cya+ crp+ were hyperinducible, and the sensitivity of each to cAMP was altered. Two models are presented that show the possible mutational lesion in the araCi strains.

Identification of the AraE transport protein of Escherichia coli

“…By contrast, araE maps near thyA at about 61 min (Brown & Hogg, 1972;Daruwalla, 1979; the present paper) and araF maps near his at about 44 min (Heffernan et al, 1976), a separation which facilitates genetic manipulation of the transport proteins. Presumably these proteins are membrane-bound, although the araF lesion has been correlated with the loss of a periplasmic binding protein (Brown & Hogg, 1972;Heffernan et al, 1976). This paper identifies a protein component of the Abbreviation used: SDS, sodium dodecyl sulphate.…”

“…The other, designated araF (Brown & Hogg, 1972), involves a binding protein (Schleif, 1969;Parsons & Hogg, 1974) and is probably energized by a phosphorylated product of glycolysis (Daruwalla, 1979). Expression of the transport genes is highly induced by arabinose through positive interaction with the product of araC (Englesberg et al, 1965;Heffernan et al, 1976); araC maps at 1 min on the E. coli genetic map with araA, araB and araD, the structural genes for the isomerase, kinase and epimerase involved in cytoplasmic metabolism of arabinose (Englesberg et al, 1965). By contrast, araE maps near thyA at about 61 min (Brown & Hogg, 1972;Daruwalla, 1979; the present paper) and araF maps near his at about 44 min (Heffernan et al, 1976), a separation which facilitates genetic manipulation of the transport proteins.…”

“…Expression of the transport genes is highly induced by arabinose through positive interaction with the product of araC (Englesberg et al, 1965;Heffernan et al, 1976); araC maps at 1 min on the E. coli genetic map with araA, araB and araD, the structural genes for the isomerase, kinase and epimerase involved in cytoplasmic metabolism of arabinose (Englesberg et al, 1965). By contrast, araE maps near thyA at about 61 min (Brown & Hogg, 1972;Daruwalla, 1979; the present paper) and araF maps near his at about 44 min (Heffernan et al, 1976), a separation which facilitates genetic manipulation of the transport proteins. Presumably these proteins are membrane-bound, although the araF lesion has been correlated with the loss of a periplasmic binding protein (Brown & Hogg, 1972;Heffernan et al, 1976).…”

Regulation of cell division and of tyrosinase in B16 melanoma cells by imidazole: A possible role for the concept of metabolite Gene regulation in mammalian cells

“…In many procaryotes, such as Escherichia coli, adenosine 3',5'-cyclic monophosphate (CAMP) is required for the induction of catabolite-repressible gene transcription (Pastan and Perlman, 1970;Zubay et al, 1970). A cAMP binding protein (CAP) in E. coli, when activated by CAMP, acts with other regulatory factors to direct and initiate mRNA polymerization (Anderson et al, 1971;Heffernan et al, 1976). Mutants ofE.…”

Expression of the maltose regulon in strains lacking the cyclic AMP receptor protein

“…Specific mutants affected in the arabinose (ara) in the D-serine deaminase (dsd) regulatory genes are able to express enzymes encoded by the ara or dsd operons in cya and crp strains [3,4]. Moreover, some of these mutants exhibit altered sensitivity to catabolite repression in a crp + background [5].…”