Publications

• The RihA, RihB, and RihC ribonucleoside hydrolases of Escherichia coli. Substrate specificity, gene expression, and regulation.

  Petersen C., Moeller L.B.

  Pyrimidine-requiring cdd mutants of Escherichia coli deficient in cytidine deaminase utilize cytidine as a pyrimidine source by an alternative pathway. This has been presumed to involve phosphorylation of cytidine to CMP by cytidine/uridine kinase and subsequent hydrolysis of CMP to cytosine and r ... >> More

  Pyrimidine-requiring cdd mutants of Escherichia coli deficient in cytidine deaminase utilize cytidine as a pyrimidine source by an alternative pathway. This has been presumed to involve phosphorylation of cytidine to CMP by cytidine/uridine kinase and subsequent hydrolysis of CMP to cytosine and ribose 5-phosphate by a putative CMP hydrolase. Here we show that cytidine, in cdd strains, is converted directly to cytosine and ribose by a ribonucleoside hydrolase encoded by the previously uncharacterized gene ybeK, which we have renamed rihA. The RihA enzyme is homologous to the products of two unlinked genes, yeiK and yaaF, which have been renamed rihB and rihC, respectively. The RihB enzyme was shown to be a pyrimidine-specific ribonucleoside hydrolase like RihA, whereas RihC hydrolyzed both pyrimidine and purine ribonucleosides. The physiological function of the ribonucleoside hydrolases in wild-type E. coli strains is enigmatic, as their activities are paralleled by the phosphorolytic activities of the nucleoside phosphorylases, and a triple mutant lacking all three hydrolytic activities grew normally. Furthermore, enzyme assays and lacZ gene fusion analysis indicated that rihB was essentially silent unless activated by mutation, whereas rihA and rihC were poorly expressed in glucose medium due to catabolite repression. << Less

  J. Biol. Chem. 276:884-894(2001) [PubMed] [EuropePMC]

• Cloning, purification, crystallization and X-ray analysis of the Escherichia coli pyrimidine nucleoside hydrolase YeiK.

  Giabbai B., Degano M.

  The E. coli yeiK gene product is homologous to members of the nucleoside hydrolase family of enzymes, the physiological role of which in bacteria is still unknown. Here, the cloning, expression in milligram quantities and enzymatic characterization of YeiK as a pyrimidine-specific nucleoside hydro ... >> More

  The E. coli yeiK gene product is homologous to members of the nucleoside hydrolase family of enzymes, the physiological role of which in bacteria is still unknown. Here, the cloning, expression in milligram quantities and enzymatic characterization of YeiK as a pyrimidine-specific nucleoside hydrolase is reported. Crystals of YeiK diffract X-rays to a resolution of 1.7 A and belong to the triclinic crystal system in space group P1, with unit-cell parameters a = 44.81, b = 85.71, c = 90.68 A, alpha = 112.95, beta = 101.95, gamma = 85.92 degrees. << Less

  Acta Crystallogr D Biol Crystallogr 60:524-527(2004) [PubMed] [EuropePMC]

• Purification and properties of nucleoside hydrolase from Pseudomonas fluorescens.

  Terada M., Tatibana M., Hayaishi O.

  J Biol Chem 242:5578-5585(1967) [PubMed] [EuropePMC]

• Crystal structure to 1.7 A of the Escherichia coli pyrimidine nucleoside hydrolase YeiK, a novel candidate for cancer gene therapy.

  Giabbai B., Degano M.

  Enzymes with nucleoside hydrolase (NH) activity are crucial for salvaging nucleic acid components in purine auxotrophic protozoan parasites, but are also present in prokaryotes and higher eukaryotes. Here we analyze the distribution of genes encoding for putative NH proteins and characterize the y ... >> More

  Enzymes with nucleoside hydrolase (NH) activity are crucial for salvaging nucleic acid components in purine auxotrophic protozoan parasites, but are also present in prokaryotes and higher eukaryotes. Here we analyze the distribution of genes encoding for putative NH proteins and characterize the yeiK gene product from Escherichia coli as a pyrimidine-specific NH. The crystal structure of YeiK to 1.7 A defines the structural basis for its substrate specificity and identifies residues involved in the catalytic mechanism that differ from both nonspecific and purine-specific NHs. Large differences in the tetrameric quaternary structure compared to nonspecific protozoan NHs are brought forth by minor differences in the interacting surfaces. The first structural and functional characterization of a nonparasitic, pyrimidine nucleoside-specific NH suggests a possible role for these enzymes in the metabolism of tRNA nucleosides. The high catalytic efficiency of YeiK toward 5-fluorouridine could be exploited for suicide gene therapy in cancer treatment. << Less

  Structure 12:739-749(2004) [PubMed] [EuropePMC]

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