InterPro domain: IPR013655

The PAS fold corresponds to the structural domain that has previously been defined as PAS and PAC motifs [ 1 ]. The PAS fold appears in archaea, eubacteria and eukarya, and is involved in a variety of functions within sensory proteins promoting protein-protein interactions, signal transfer or as a stimuli sensor [ 2 ]. The PAS domain contains a sensory box, or S-box domain that occupies the central portion of the PAS domain but is more widely distributed. It is often tandemly repeated. Known prosthetic groups bound in the S-box domain include haem in the oxygen sensor FixL [ 3 ], FAD in the redox potential sensor NifL [ 4 ], and a 4-hydroxycinnamyl chromophore in photoactive yellow protein [ 5 ]. Proteins containing the domain often contain other regulatory domains such as response regulator or sensor histidine kinase domains. Other S-box proteins include phytochromes and the aryl hydrocarbon receptor nuclear translocator.

This domain has been found in the gene product of the madA gene of the filamentous zygomycete fungus Phycomyces blakesleeanus. It has been shown that MadA encodes a blue-light photoreceptor for phototropism and other light responses. The gene is involved in the phototropic responses associated with sporangiophore growth; they exhibit phototropism by bending toward near-UV and blue wavelengths and away from far-UV wavelengths in a manner that is physiologically similar to plant phototropic responses [ 6 ].

1. The PAS fold. A redefinition of the PAS domain based upon structural prediction. Eur. J. Biochem. 271, 1198-208
2. Ligand-binding PAS domains in a genomic, cellular, and structural context. Annu. Rev. Microbiol. 65, 261-86
3. Role of distal arginine in early sensing intermediates in the heme domain of the oxygen sensor FixL. Biochemistry 45, 6018-26
4. Role of the central region of NifL in conformational switches that regulate nitrogen fixation. Biochem. Soc. Trans. 34, 162-4
5. Resonance Raman spectroscopy reveals the origin of an intermediate wavelength form in photoactive yellow protein. Biochemistry 43, 2279-87
6. The Phycomyces madA gene encodes a blue-light photoreceptor for phototropism and other light responses. Proc. Natl. Acad. Sci. U.S.A. 103, 4546-51