Ureidosuccinate is transported by the allantoate transport system in Saccharomyces cerevisiae

The regulatory characteristics exhibited by ureidosuccinate transport in Saccharomyces cerevisiae led us to hypothesize that this biosynthetic intermediate was transported via the degradative allantoate transport system. The hypothesis was verified by the finding that neither dal5 nor urep1 mutant strains could transport allantoate or ureidosuccinate. Mutations in the two loci were tightly linked and failed to complement one another, suggesting that they were allelic. The use of a common transport system for accumulation of both biosynthetic and degradative metabolites explains the paradoxical characteristics observed for control of ureidosuccinate and allantoate transport.