FIG. 4.

(A) Enhanced utilization of potassium nitrate by the Δtar1 mutant. H99 and the Δtar1C strain produced petite colonies in the presence of 7% KNO₃ as the only nitrogen source (upper panels). The Δtar1 mutant showed high sensitivity to 200 mM KClO₃ under nitrogen-limiting conditions (5 mM ammonium tartrate). A total of 10³ cells in suspension were dropped onto Asn salt agar with 2% glucose at 30°C. (B) Alignment of the Rossmann fold for fungal Nmr proteins and the human HSCARG protein. Cryptococcal Tar1 and HSCARG have a typical Rossmann motif conserved in the members of the family, while Nmr1 and NmrA have variations in the sequence. An unknown HXXXK motif (where X is any amino acid residue) was also found in Tar1. The numbers in the sequences indicate the positions of the motifs in each protein.