InterPro domain: IPR035965

PAS domains are involved in many signalling proteins where they are used as a signal sensor domain [ 1 ]. PAS domains appear in archaea, bacteria and eukaryotes. Several PAS-domain proteins are known to detect their signal by way of an associated cofactor. Heme,flavin, and a 4-hydroxycinnamyl chromophore are used in different proteins. The PAS domain was named after three proteins that it occurs in:

• Per- period circadian protein
• Arnt- Ah receptor nuclear translocator protein
• Sim- single-minded protein.

PAS domains are often associated with PAC domains IPR001610 . It appears that these domains are directly linked, and that together they form the conserved 3D PAS fold. The division between the PAS and PAC domains is caused by major differences in sequences in the region connecting these two motifs [ 2 ]. In human PAS kinase, this region has been shown to be very flexible, and adopts different conformations depending on the bound ligand [ 3 ]. Probably the most surprising identification of a PAS domain was that in EAG-like K -channels [ 4 ].

1. PAS domains: internal sensors of oxygen, redox potential, and light. Microbiol. Mol. Biol. Rev. 63, 479-506
2. The PAS fold. A redefinition of the PAS domain based upon structural prediction. Eur. J. Biochem. 271, 1198-208
3. Structure and interactions of PAS kinase N-terminal PAS domain: model for intramolecular kinase regulation. Structure 10, 1349-61
4. PAS domain S-boxes in Archaea, Bacteria and sensors for oxygen and redox. Trends Biochem. Sci. 22, 331-3