title: Crystal structure to 1.7 a of the Escherichia coli pyrimidine nucleoside hydrolase YeiK, a novel candidate for cancer gene therapy.
abstract: 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.
authors.affiliation: Biocrystallography Unit, DIBIT, San Raffaele Scientific Institute, via Olgettina 58, I-20132 Milan, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Giabbai
authors.forename: Massimo
authors.initials: M
authors.lastname: Degano
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000737:chemistry* / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics; D015316:Genetic Therapy; D008969:Molecular Sequence Data; D009154:Mutation; D009699:N-Glycosyl Hydrolases / Q000737:chemistry* / Q000235:genetics; D009369:Neoplasms / Q000628:therapy*; D017434:Protein Structure, Tertiary
chemical_list: D029968:Escherichia coli Proteins; D009699:N-Glycosyl Hydrolases; C422988:RihB protein, E coli