IRE1 encodes a putative protein kinase containing a membrane-spanning domain and is required for inositol phototrophy in Saccharomyces cerevisiae.

A novel gene, IRE1, of Saccharomyces cerevisiae was cloned through genetic complementation of a myoinositol auxotrophic mutant. The predicted amino acid sequence indicated that IRE1 encodes a protein of 126983 Da with two highly hydrophobic regions, probably a signal sequence and a membrane-spanning region. The carboxy-terminal region of IRE1 showed close sequence similarity to the catalytic domains of protein kinases. Disruption of the IRE1 locus caused myo-inositol auxotrophy. The IRE1 product is very likely a protein kinase required for myo-inositol synthesis.