Abstract

Uridine kinase (UK) and uracil phosphoribosyltransferase (UPRT) are enzymes in pyrimidine salvage pathway. UK or UPRT were reported as separate genes in bacteria. Amino acid sequence of OsUK/UPRT1 from rice shows homology to bacterial enzymes. Amino-terminal region is similar to UDK with an ATP/GTP-binding motif, whereas the carboxyl-terminal similar to UPP with two binding motifs for a uracil and a PRPP, respectively. Expression of OsUK/UPRT1 in an udk and/or upp mutant of Escherichia coli led to growth inhibition with 5-fluorouridine or 5-fluorouracil. These results suggest that the OsUK/UPRT1 product would be a natural fusion protein of two enzymes.

Key words: 5-Fluorouracil, 5-fluorouridine, Oryza sativa, uridine kinase, uracil phosphoribosyltransferase.

Abbreviation

UK, Uridine kinase; UPRT, uracil phosphoribosyltransferase;PRPP, 5-phosphoribosyl-1-pyrophosphate; 5-FD, 5-fluorouridine; 5-FU, 5-fluorouracil; CTP, cytidine 5’-triphosphate; UMP, uridine 5’-monophosphate; ATP,adenosine 5-triphosphate; UTP, uridine 5’-triphosphate; GTP, guanosine 5’-triphosphate; UDK , uridine kinase in bacteria; MM-Ura, minimal medium without Ura; ORF, open reading frame; PCR, polymerase chain reaction; RGRC, rice genome resource center; EMBL, European molecular biology laboratory; BLAST,basic local alignment search tool; Clustal W, clustal weights program.