Identification of the molecular mechanisms by which the diterpenoid salvinorin A binds to kappa-opioid receptors.
Feng Yan, Philip D Mosier, Richard B Westkaemper, Jeremy Stewart, Jordan K Zjawiony, Timothy A Vortherms, Douglas J Sheffler, Bryan L. Roth
Biochemistry June 21, 2005 DOI: 10.1021/bi050490d (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Experimental study Peer reviewed |
|---|---|
| Topics | Salvia divinorum |
| Keywords | Opioid receptors Opioid receptor binding Receptor activation Receptor selectivity Receptor pharmacology Hallucinogens Natural hallucinogen Psychoactive compounds Ligand Molecular mechanisms Binding mechanism Molecular pharmacology Tyrosine residues Binding sites Activation mechanism Unique binding Selective activation Drug discovery Compound modification Affinity enhancement Novel technique Drug development |
| Citations | 91 |
| Key findings | Salvinorin A selectively activates kappa-opioid receptors through unique interactions with specific tyrosine residues in the binding pocket, distinct from those required by nitrogenous and peptidergic agonists. |
Abstract
Salvinorin A is a naturally occurring hallucinogenic diterpenoid from the plant Salvia divinorumthat selectively and potently activates kappa-opioid receptors (KORs). Salvinorin A is unique in that it is the only known lipid-like molecule that selectively and potently activates a G-protein coupled receptor (GPCR), which has as its endogenous agonist a peptide; salvinorin A is also the only known non-nitrogenous opioid receptor agonist. In this paper, we identify key residues in KORs responsible for the high binding affinity and agonist efficacy of salvinorin A. Surprisingly, we discovered that salvinorin A was stabilized in the binding pocket by interactions with tyrosine residues in helix 7 (Tyr313 and Tyr320) and helix 2 (Tyr119). Intriguingly, activation of KORs by salvinorin A required interactions with the helix 7 tyrosines Tyr312, Tyr313, and Tyr320 and with Tyr139 in helix 3. In contrast, the prototypical nitrogenous KOR agonist U69593 and the endogenous peptidergic agonist dynorphin A (1-13) showed differential requirements for these three residues for binding and activation. We also employed a novel approach, whereby we examined the effects of cysteine-substitution mutagenesis on the binding of salvinorin A and an analogue with a free sulfhydryl group, 2-thiosalvinorin B. We discovered that residues predicted to be in close proximity, especially Tyr313, to the free thiol of 2-thiosalvinorin B when mutated to Cys showed enhanced affinity for 2-thiosalvinorin B. When these findings are taken together, they imply that the diterpenoid salvinorin A utilizes unique residues within a commonly shared binding pocket to selectively activate KORs.