Characterization of the Escherichia coli codBA operon encoding cytosine permease and cytosine deaminase

Abstract

The nucleotide sequence of a 3.1 kb segment carrying the cytosine deaminase gene (codA) from Escherichia coli was determined. The sequence revealed the presence of two open reading frames, the first (codB) specifying a highly hydrophobic polypeptide and the second specifying cytosine deaminase. A two-codon overlap between the two reading frames indicates that they constitute an operon. Transcription of the operon was found to be regulated by exogenous purines. Polypeptides specified by each of the two reading frames were expressed in minicells, and the codB gene product was found to be highly enriched in the membrane fraction. Uptake experiments showed that the CodB protein is required for cytosine transport into the cell and that the intracellular accumulation of cytosine correlated with the codB gene dose. A topological model for the cytosine permease in the cytoplasmic membrane is proposed.

Repurposing the antimycotic drug flucytosine for suppression ofPseudomonas aeruginosapathogenicity

“…com), encoding a cytosine deaminase and a cytosine permease, respectively (20). To assess whether conversion to 5-fluorouracil is essential for the antipyoverdine activity of 5-FC, we tested 5-FC against individual P. aeruginosa codA and codB deletion mutants.…”

Modified vaccinia virus Ankara as a vector for suicide gene therapy

“…Currently, one of the most efficient and extensively studied prodrug activation systems is the bacterial cytosine deaminase (CDase) in combination with 5-fluorocytosine (5-FC). [1][2][3][4][5][6][7] CDase, an enzyme present in fungi and bacteria 8,9 but absent in mammalian cells, 10 deaminates the nontoxic prodrug 5-FC to its highly toxic derivative 5-fluorouracil (5-FU).…”

Enhanced suicide gene effect by adenoviral transduction of a VP22-cytosine deaminase (CD) fusion gene

“…4 CD is found in many bacteria, yeast and fungi, where it deaminates cytosine to uracil. 5 It also deaminates the relatively non-toxic prodrug 5-fluorocytosine (5-FC) to the highly toxic 5-fluorouracil (5-FU), widely used in the treatment of solid malignant tumours. Transduction of the CD gene into tumour cells combined with a systemic administration of 5-FC has been shown to have anticancer effects in various animal models.…”