Correction to: Nature online 23 October 2019

In Fig. 1 of this Article, the label for residue 24 in peptide 4 should have been ‘Thr’ instead of ‘Dab’, and in peptide 5, the labels for the ‘N’ and ‘C’ termini should have been reversed (with the C terminus next to Dab, and the N terminus next to Trp). This figure has been corrected online.