Full Length Research Paper

Expression of a natural fusion gene for uracil phosphoribosyltransferase and uridine kinase from rice shows growth retardation by 5-fluorouridine or 5-fluorouracil in Escherichia coli

Md. Shafiqul Islam Sikdar and Jung-Sup Kim*

Faculty of Biotechnology, Jeju National University, Jeju, 690 - 756, Republic of Korea.

*Corresponding author. E-mail: biotech2020@jejunu.ac.kr. Tel: +82-64-754-3393. Fax: +82-64-754-3393.

Abbreviations: 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.

Accepted 26 January, 2010

   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.