Basic domains Basic helix-loop-helix factors (bHLH) CLASSLINK:http\://www.edgar-wingender.de/class 1.2.html Class TRANSFAC class description C0010: A DNA-binding basic region is followed by a motif of two potential amphipathic alpha-helices connected by a loop of variable length, possibly an omega loop. This putative helix-loop-helix (HLH) motif mediates dimerization as a prerequisite for DNA-binding. Upon dimerization, the alpha-helical content may significantly increase supporting the model of a four-helix bundle dimerization interface. Probably, the HLH domains of both dimer constituents are arranged in a parallel orientation. The basic region dictates DNA-binding specificity. Upon DNA-binding of the dimer, the basic regions adopt alpha-helical conformation as well.