Biomedical Engineering Reference
In-Depth Information
Fig. 7.4
Steroid receptors, zinc fi ngers and DNA binding
interactions between two signaling pathways can increase duration of signals; and
negative interactions between pathways can block signals.
A .
Generalized structure of all steroid hormone receptors showing the different
domains
,
location of the zinc fi ngers and the regions of the receptor responsible
for transcriptional activity
(
TAF
).
B .
Two
-
dimensional structure of the zinc fi ngers of the DNA binding domain
(
DBD
)
in a single receptor. I
,
II and III indicate the helical regions of the DBD. The fi rst
helix contains the P box which determines the specifi city of the DNA binding.
The three amino acids that determine whether the receptor will combine with a
glucocorticoid response element
(
GRE
)
or an estrogen response element
(
ERE
)
on the DNA are indicated. Arrows indicate the different amino acids that convert
GRE specifi city to ERE specifi city. Amino acids shown as solid circles indicate
those that are important for dimerization of two receptors
.
C .
Diagram showing dimerization of two receptors and helix I of each receptor
slotting into the helix of the DNA. The base sequences of the ERE and GRE are
shown plus the palindromic sequence. An example of a direct repeat sequence is
also shown
.
The functions of hormones as regulatory, controlling molecules in the body can be
broadly grouped into several categories: reproduction and sexual differentiation;
development and growth; maintenance of the internal environment; and regulation of
metabolism and nutrient supply. A single hormone may affect more than one of these
