Cloning and disruption of the YNR1 gene encoding the nitrate reductase apoenzyme of the yeast Hansenula polymorpha.

The nitrate reductase gene (YNR1) from the yeast H. polymorpha was isolated from a lambda EMBL3 genomic DNA library. As probe a 350 bp DNA fragment synthesized by PCR from H. polymorpha cDNA was used. By DNA sequencing an ORF of 2,577 bp was found. The predicted protein has 859 amino acids and presents high identity with nitrate reductases from other organisms. Chromosomal disruption of YNR1 causes inability to grow in nitrate. Northern blot analysis showed that YNR1 expression is induced by nitrate and repressed by ammonium.