J. Biol. Chem., Vol. 255, Issue 17, 8035-8037, Sep, 1980
Reversible dissociation of steroid hormone x receptor complexes by mercurial reagents
WA Coty
Steroid hormone receptors contain a reactive sulfhydryl group (or groups)
required for hormone binding. In the present study, the effects of several
sulfhydryl-blocking reagents on hormone binding to aporeceptors and hormone
x receptor complexes were compared, with the use of preparations of chick
oviduct progesterone receptor and intestinal vitamin D receptor.
N-Ethylmaleimide inhibited hormone binding to aporeceptors, whereas prior
hormone binding protected against inactivation. In contrast, the mercurial
reagent mersalyl both inhibited hormone binding to aporeceptors and
dissociated hormone x receptor complexes. Complete dissociation of these
complexes was achieved within 20 to 30 min at 0 degrees C. This process was
a pseudo- first order reaction with a t 1/2 much less than the t 1/2 for
hormone dissociation for either receptor at 0 degrees C. Hormone
displacement was a general property of mercurial reagents; several organic
mercurials as well as HgCl2 were effective. In contrast, sulfhydryl-
alkylating agents (maleimides, iodoacetamide) and the disulfide 5,5'-
dithiobis(2-nitrobenzoate) were ineffective in displacing bound hormone
from either progesterone or vitamin D receptors. Finally, hormone
displacement by mersalyl was reversible; addition of excess thiol reagent
displaced the bound mersalyl and regenerated hormone binding activity in
good yield. This result suggests that mercurial reagents should prove
useful in further study of steroid hormone receptors, for example in
elution of receptors from steroid-affinity adsorbents.