Binding of steroids to the cytoplasmic receptor of the embryonic chick retina: Kinetics and structural considerations

Abstract

The retina of the 12-day embryonic chick contains cortisol-binding proteins. The 3-ketone group on the steroid molecule was found to be essential for receptor binding. The 11 β-hydroxyl group, which is considered to be of primary importance in the induction of the retinal enzyme glutamyltransferase, does not affect receptor binding. The 17-group on the steroid can, in some cases, influence receptor binding as well as the enhancement of glutamyltransferase activities. These receptors exhibit a high degree of affinity for the steroid and bind rapidly to the steroid, saturating within 1 h at 0 ° to 4 °C at approximately 10 −8 m with a K d of ⋍ 10 −9 m.