Fig. 6.

A proposed functional classification scheme of PAS protein interactions. The alpha class (reds) includes those proteins that often have restricted cell specific expression and bind with beta class proteins, often in response to an environmental stimulus or cellular state. The beta class (blues), are more widely expressed and act as binding partners for proteins from multiple PAS families, especially alpha class. The delta class (pinks) includes proteins that are often considered repressors and harbor deletions of classical domains such as PAS-B or bHLH. The gamma class (orange), include the mammalian coactivators (NCOAs) and are known for their unique role in transcriptional modulation. Finally, we show two PAS protein families that were not discussed in detail in this review; The epsilon class (purple), includes enzymes with PAS domains, while the kappa class (green) includes potassium channels. The bHLH, PAS A and PAS B domains are depicted as A and B respectively in the proteins in which they adhere to motifs as designated by UNIPROT [191].