Structure of the rudimentary-like gene and UMP synthase in Drosophila melanogaster.

The last two steps of de novo UMP biosynthesis are performed by a bi-enzymic protein in animal cells, UMP synthase, that is encoded by the gene r-l in Drosophila melanogaster. Over 3.5 kb of genomic DNA spanning this gene were sequenced. Transcriptional organization of r-l has been determined by sequence analysis of two cDNA clones and by primer extension analysis of embryonic RNA. The DNA region 5' to the apparent transcription start point contains no known transcriptional control elements or sequences similar to those upstream from dhod, which encodes the metabolic pathway step preceding UMP synthase. The deduced protein of 53.5 kDa is similar to the UMP synthases of slime molds and humans. It contains the two enzymatic domains separated by an apparent bridge polypeptide sequence of over 30 amino acids, which is dissimilar among UMP synthases of different organisms. The r-l structure includes two introns, one of which occurs within the DNA region that encodes the interdomain bridge sequence of the protein.