PhASER epitope mapping of RXFP1. The RXFP1 peptide is noted at the bottom, with the identified epitope outlined (black box), identified by areas where mutagenesis caused a loss or reactivity (red) as measured by fold enrichment over input library using various approaches denoted on the left axis (single alanine scanning and 6-mer blocks of alanine scanning), as well as stop scanning mutagenesis, used to define the epitope boundary (line above the figure).