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

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.