-  Superclass
-  Basic domains
-  "TRANSFAC class description C0033: Proteins belonging to this superfamily contact the DNA through a basic region which free in solution has a random structure, but becomes alpha-helically folded upon binding to DNA (PMID 2120592, PMID 2145515, PMID 1312255, PMID 8479534, PMID 7926781). Most prominent classes of this group are the bZIP and bHLH proteins. There is no 'consensus' motif for all basic domains of this superfamily. Even the basic regions of bZIP and bHLH factors diverge greatly, although their mode of interacting with the DNA is strictly homologous: A specific alpha-helical dimerization domain provides the linkage between two DNA-contacting basic regions which adopt helical conformation when their positively charged side chains are neutralized by the phosphate backbone of the DNA."