Molecular and General Genetics MGG

, Volume 126, Issue 2, pp 177–186

Mutants of Escherichia coli unable to metabolize cytidine: Isolation and characterization

Authors

  • Karin Hammer-Jespersen
    • Institute of Biological Chemistry BUniversity of Copenhagen
  • Agnete Munch-Petersen
    • Institute of Biological Chemistry BUniversity of Copenhagen
Article

DOI: 10.1007/BF00330992

Cite this article as:
Hammer-Jespersen, K. & Munch-Petersen, A. Molec. gen. Genet. (1973) 126: 177. doi:10.1007/BF00330992

Summary

Strains of Escherichia coli have been selected, which contain mutations in the udk gene, encoding uridine kinase. The gene has been located on the chromosome as cotransducible with the his gene and shown to be responsible for both uridine and cytidine kinase activities in the cell.

An additional mutation in the cdd gene (encoding cytidine deaminase) has been introduced, thus rendering the cells unable to metabolize cytidine. In these mutants exogenously added cytidine acts as inducer of nucleoside catabolizing enzymes indicating that cytidine per se is the actual inducer.

When the udk, cdd mutants are grown on minimal medium the enzyme levels are considerably higher than in wild type cells. Evidence is presented indicating that the high levels are due to intracellular accumulation of cytidine, which acts as endogenous inducer.

Abbreviations and Symbols

FU

5-fluorouracil

FUR

5-fluorouridine

FUdR

5-fluoro-2'deoxyuridine

FCR

5-fluorocytidine

FCdR

5-fluorodeoxycytidine

THUR

3, 4, 5, 6-tetrahydrouridine

UMP

uridine monophosphate

CMP

cytidine monophosphate

dUMP

deoxyuridine monophosphate. Genes coding for: cytidine deaminase

edd

uridine phosphorylase

udp

thymidine phosphorylase

tpp

purmnucleoside phosphorylase

pup

uridine kinase (=cytidine kinase)

udk

UMP-pyrophosphorylase

upp. CytR

regulatory gene for cdd, udp, dra, tpp, drm and pup

Enzymes

EC 2.4.2.1

Purine nucleoside phosphorylase or purine nucleoside: orthophosphate (deoxy)-ribosyltransferase

EC 2.4.2.4

thymidine phosphorylase or thymidine: orthophosphate deoxyribosyltransferase

EC 2.4.2.3

uridine phosphorylase or uridine: orthophosphate ribosyltransferase

EC 3.5.4.5

cytidine deaminase or (deoxy)cytidine aminohydrolase

EC 4.1.2.4

deoxyriboaldolase or 2-deoxy-D-ribose-5-phosphate: acetaldehydelyase

EC 2.4.2.9

UMP-pyrophosphorylase or UMP: pyrophosphate phosphoribosyltransferase

EC 2.7.1.48

uridine kinase or ATP: uridine 5′-phosphotransferase

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Copyright information

© Springer-Verlag 1973