A ubiquitous protein module (Per–Arnt–Sim domain) in which the structure but not sequence is conserved. PAS domains regulate the function of many intracellular signalling pathways through protein-protein interactions or by binding cofactors. See period and ARNT (aryl hydrocarbon receptor nuclear translocator). PAS kinase (PASK, 1323 aa) is an evolutionarily conserved serine/threonine kinase that may phosphorylate and inactivate muscle glycogen synthase.
http://pawsonlab.mshri.on.ca/index.php?option=com_content&task=view&id=207&Itemid=64 Structure and details.