Binding to a response element

Many hormones and growth factors activate
cell-surface receptors. In contrast, steroid hormones
enter the target cells and interact there
with a specific receptor protein in the cytosol.
The hormone–receptor complex then migrates
to specific sites of DNA. The hormone-binding
domain will prevent binding to DNA unless the
hormone is present. Activated receptors bind to
specific DNA sequences called hormone response
elements (HREs). Each polypeptide
chain of the receptor contains a zinc atom
bound to four cysteines (1). The skeletal model
shows the two DNA-binding domains binding
to the HRE in two adjacent major grooves of the
target DNA (2). The space-filling model shows
how tightly the recognition helix of each dimer
of this protein fits into the major groove of DNA
shown in red and green