Deep mutational scanning of the cross-reactive motif between DIP2A and HHV6 U27. The heatmap denotes the impact of point mutation at each position in the motif HHV6 U27, residues 8–16 (x axis) relative to each point mutant (y axis), which are grouped by properties of their side chains (1, acidic/negative charge; 2, basic/positive charge; 3, polar, uncharged; and 4, hydrophobic). Data are expressed as a percentage of the wild-type U27 reactivity (mutational tolerance, legend at right). Average mutational tolerance at each position of the motif is summarized at the top of the heatmap.