Ecdysteroid receptors: a comparison of cytoplasmic and nuclear receptors from crayfish hypodermis.

Cytoplasmic and nuclear ecdysteroid receptors from intermolt Orconectes limosus integument have been compared. The specificities as well as the KD values for three [3H]ecdysteroids are very similar in both preparations. Using a photoaffinity labelling technique, the molecular mass of the hormone-receptor complexes from both preparations was determined by sodium dodecyl sulfate-gel electrophoresis as 70 000 Da. The isoelectric points are about 6 in both cases. Nuclear receptor can be extracted by 0.4M KCl. The binding can be completely restored if cytosol from the same source is incubated together with nuclei and [3H]20-hydroxyecdysone, but not if denatured cytosol or bovine serum albumin is used.