Thus a local conformational change initiated by the agonist, but not antagonist binding results in a destabilization of the protein structure. This destabilization is not strong enough to denature the protein, but results in a long range effect across the protein affecting its active site several angstrom away from the ligand binding site. This is known as an allosteric mechanism. As a rule, agonists induce structure destabilization, while antagonists merely bind , but do not affect the protein structure (or trigger a conformational change that locks a protein in its inactive position). One way to visualize the action of ligands on receptors is to realize that proteins constantly undergo conformational changes which is best described as an equilibrium between an active and inactive, or even among multiple states, including desensitized states (different types of inactive states). Agonists and antagonists shift this equilibrium towards an active or inactive conformation, respectively.
Cells of the zona fasciculata and zona reticularis lack aldosterone synthase (CYP11B2) that converts corticosterone to aldosterone, and thus these tissues produce only the weak mineralocorticoid corticosterone. However, both these zones do contain the CYP17A1 missing in zona glomerulosa and thus produce the major glucocorticoid, cortisol. Zona fasciculata and zona reticularis cells also contain CYP17A1, whose 17,20-lyase activity is responsible for producing the androgens, dehydroepiandosterone (DHEA) and androstenedione. Thus, fasciculata and reticularis cells can make corticosteroids and the adrenal androgens, but not aldosterone.
Copyright text 2016 by Anabolic Health.
is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to . Additionally, participates in various other affiliate programs, and we sometimes get a commission through purchases made through our links.
Use of this website constitutes acceptance that the material appearing on is for educational use only and should not be used as a substitute for professional medical advice, diagnosis or treatment.