Correction to: Nature https://doi.org/10.1038/s41586-019-1604-6 Published online 25 September 2019

In the version of this article originally published, due to a figure preparation error following peer review, information in Extended Data Fig. 2e was a duplicate of Extended Data Fig. 6a. Extended Data Fig. 2e and Extended Data Fig. 6a both show the maximum conserved residues around retinal and their conservation ratios in HeR family members, while Extended Data Fig. 2e should instead have shown the conserved residues and their conservation ratios in the HeR family members. Upon finding this error, we also noted that the transmembrane helix labelling in Fig. 1 is incorrect, with the current labels TM4 (lower) and TM6 (higher) incorrectly switched.

Due to the age of the paper, these figures cannot be updated directly. The Supplementary Information accompanying this amendment contains the corrected Extended Data Fig. 2e and Fig. 1, and serves to correct the article.

Supplementary information is available in the online version of this amendment.