basic helix-loop-helix (bHLH) domain found in Saccharomyces cerevisiae phosphate system positive regulatory protein PHO4 and similar proteins
PHO4 is a transcriptional activator that regulates the expression of repressible phosphatase under phosphate starvation conditions in Saccharomyces cerevisiae. The PHO4 protein has four functional domains with the bHLH domain at its carboxyl-terminal region. It regulates transcription by binding to promoter of the genes as a homodimer.