Extended Data Fig. 1. Snake plot of the µOR sequence.

Cysteine residues in yellow indicate native cysteine that were kept in the labeling constructs. Residues in green indicate native cysteine that is mutated to corresponding residues to avoid nonspecific labeling by cysteine reactive labeling reagent. Residues in red indicate labeling sites that are mutated to cysteine for labeling with cysteine-reactive fluorophores and nitroxide spin labels.