Steroids act via nuclear receptors which interact with DNA through
Binding of transcription regulatory proteins to DNA is regulated by several motifs :


Helix turn helix
Leucine zipper
Zinc finger



Binding motif for steroid receptor family & thyroid (nuclear) receptor family is a zinc finger.
In proteins with zinc - finger motif, the binding site is repeated 2-9 times.
Proteins with helix-turn-helix and leucine zipper motifs form symmetrical palindromes and their DNA binding sites are symmetrical palindromes.

In leucine - zipper motif, there is a periodic repeat of a leucine residue at every 7th position
Helix turn helix
Zinc finger motif
Histidine
Leucine zipper