An Arabidopsis cDNA encoding a bifunctional glutamine amidotransferase/cyclase suppresses the histidine auxotrophy of a Saccharomyces cerevisiae his7 mutant.

A cDNA encoding a glutamine amidotransferase and cyclase catalyzing the fifth and sixth steps of the histidine (His) biosynthetic pathway has been isolated from Arabidopsis thaliana. The N- and C-terminal domains of the primary structure deduced from a full-length Arabidopsis hisHF (At-HF) cDNA showed significant homology to the glutamine amidotransferase and cyclase of microorganisms, respectively. Effective suppression of the His auxotrophy of a Saccharomyces cerevisiae his7 mutant with the At-HF cDNA confirmed that the At-HF protein has bifunctional glutamine amidotransferase (HisH) and cyclase (HisF) activities.