One Amino Acid Controls Which Drugs the Delta Opioid Receptor Prefers | Research

The takeaway

Mutating aspartic acid 95 to asparagine in the delta opioid receptor eliminated selective agonist binding while preserving antagonist binding — pinpointing the key residue for drug selectivity.

Single residue
Asp95→Asn mutation eliminated selective agonist binding while preserving antagonist binding — one amino acid controls selectivity

What the researchers found

Asp95Asn mutation in delta opioid receptor eliminated selective high-affinity agonist binding while preserving antagonist binding. Single residue determines agonist selectivity.

Why it matters

Knowing exactly which amino acid controls agonist selectivity enables rational design of new opioid drugs with specific receptor preferences, potentially reducing side effects.

How the study worked

Site-directed mutagenesis of the cloned delta opioid receptor. Mutant and wild-type receptors expressed in cells. Binding assays with selective agonists and antagonists.

What this study cannot tell us

In vitro study using expressed receptors in cell lines. Single point mutation may have additional uncharacterized effects. Does not demonstrate in vivo consequences.

How to read the evidence

Moderate — in vitro study with clear mutagenesis results. Strong molecular evidence but functional consequences in vivo not tested.

When this study was published

Published in 1993 (33 years ago). This finding has informed decades of opioid receptor structural biology and drug design.

The bigger picture

Knowing which single amino acid controls drug selectivity is a goldmine for drug design. It enables scientists to rationally engineer drugs that target specific opioid receptor types, potentially creating painkillers with fewer side effects.

Questions still open

Can drugs be designed to interact specifically with Asp95 for enhanced delta selectivity?
Do similar single-residue selectivity switches exist in mu and kappa receptors?

Common questions

Why does one amino acid matter so much?

Opioid receptors are protein structures where drugs fit into a binding pocket. Asp95 sits right in the pocket where agonists bind. Changing it to a slightly different amino acid disrupts the fit for agonists but not antagonists.

How does this help make better drugs?

If scientists know exactly which part of the receptor determines drug selectivity, they can design drugs that fit that specific site perfectly — creating medications that target one opioid receptor type without affecting the others.

Read the original research

A single residue, aspartic acid 95, in the delta opioid receptor specifies selective high affinity agonist binding.

The Journal of biological chemistry, 268(31), 23055-8

View on PubMed ↗

Citation

Kong, H; Raynor, K; Yasuda, K; Moe, S T; Portoghese, P S; Bell, G I; Reisine, T. (1993). A single residue, aspartic acid 95, in the delta opioid receptor specifies selective high affinity agonist binding.. The Journal of biological chemistry, 268(31), 23055-8.