Helix-turn-helix domains Tryptophan cluster factors CLASSLINK:http\://www.edgar-wingender.de/class 3.5.html Class TRANSFAC^® class description C0022: The tryptophan clusters comprise several tryptophan residues with a spacing of 12-21 amino acid residues; the subclass of myb-type DNA-binding domains typically exhibit a spacing of 19-21 amino acid residues. All IRF family members, except IRF-1 and IRF-2, contain conserved IAD, IRF association domain that is responsible for protein-protein interactions with other IRF family members or with Ets factor PU.1 and/or bHLH factor E47. IRF-1 and IRF-2 contain IAD2 that is conserved between them and, like IAD, involved in protein-protein interactions. (PMID 10586038)