Regulation of the deo operon in Escherichia coli: the double negative control of the deo operon by the cytR and deoR repressors in a DNA directed in vitro system. |
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Authors: | Poul Valentin-Hansen Bo Ahlquist Svenningsen Agnete Munch-Petersen and Karin Hammer-Jespersen |
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Institution: | (1) University Institute of Biological Chemistry B, 83, Sølvgade, DK-1307 Copenhagen K, Denmark |
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Abstract: | Summary The synthesis of the four enzymes of the deo operon in Escherichia coli is known from in vivo experiments to be subject to a double negative control, exerted by the products of the cytR and deoR genes.A DNA-directed in vitro protein synthesizing system makes the deo enzymes (exemplified by thymidine phosphorylase) in agreement with in vivo results. Enzyme synthesis is stimulated by cyclic AMP and repressed by the cytR and deoR gene products. Repression by the cytR repressor is reversed by cytidine or adenosine in the presence of cyclic AMP, while repression by the deoR repressor is reversed by deoxyribose-5-phosphate.Assays for the presence of the cytR and deoR repressors were established by use of S-30 extracts prepared from the regulatory mutants.Dissociation constants for repressor-operator binding as well as for repressor-inducer interactions have been estimated from the results.Abbreviations and Symbols
deoA (previously designated tpp)
Genes coding for: thymidine, phosphorylase
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deoB (previously designated drm)
deoxyribomutase
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deoC (previously designated dra)
deoxyriboaldolase
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deoD (previously designated pup)
purine nucleoside phosphorylase
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udp
uridine phosphorylase
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cytR
regulatory gene for cdd, udp, deoC, deoA, deoB, and deoD
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deoR (previously designated nucR)
regulatory gene for deoC, deoA, deoB, and deoD
Enzymes (EC 2.4.2.1)
Purine nucleoside phosphorylase or purine nucleoside: orthophosphate(deoxy)ribosyltansferase
- (EC 2.4.2.4)
thymidine phosphorylase or thymidine: orthophosphate deoxyribosyltransferase
- (EC 2.4.2.3)
uridine phosphorylase or uridine: orthophosphate ribosyltransferase
- (EC 4.1.2.4)
deoxyriboaldolase or 2-deoxy-D-ribose-5-phosphate: acetaldehydelyase
- (EC 2.7.5.6)
phosphodeoxyribomutase
The deo operon is defined as the gene cluster consisting of deoC deoA deoB deoD. The deo enzymes are the four enzymes encoded by the four genes of the deo operon. cAMP: cyclic adenosine 3,5-monophosphate. CRP: cyclic AMP receptor protein. dRib-5P: deoxyribose-5-phosphate. THUR: 3,4,5,6-tetrahydrouridine; EDTA: ethylene-diamine-tetra-acetate. |
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