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 via PubMed
Summary
AI-generated from the abstractSalvinorin A, a hallucinogenic compound from the plant Salvia divinorum, selectively and potently activates kappa-opioid receptors (KORs), making it the only known lipid-like molecule to do so and the only non-nitrogenous opioid receptor agonist. Key residues in KORs responsible for its high binding affinity and agonist efficacy were identified: interactions with tyrosine residues in helix 7 (Tyr313 and Tyr320) and helix 2 (Tyr119) stabilize salvinorin A in the binding pocket, while activation requires interactions with helix 7 tyrosines Tyr312, Tyr313, and Tyr320 and with Tyr139 in helix 3.
Study at a glance
| Characteristics | Experimental study Peer reviewed |
|---|---|
| Keywords | Opioid receptors Opioid receptor binding Receptor activation Receptor selectivity Receptor pharmacology |
| Citations | 91 |
| Key finding | 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.