basic Helix-Loop-Helix (bHLH) domain found in Saccharomyces cerevisiae INO4 and similar proteins
INO4 is a bHLH transcriptional activator of phospholipid synthetic genes (such as INO1, CHO1/PSS, CHO2/PEM1, OPI3/PEM2, etc.). It is required for de-repression of phospholipid biosynthetic gene expression in response to inositol deprivation in yeast. INO4 dimerizes with INO2 and binds to an UAS DNA element to control expression of the genes whose expression is inositol-responsive.