“…The significance of incorporating interactions between mutations at different residues has been demonstrated in multiple previous studies for inferring protein fitness landscapes (Sohail et al, 2021;Hart and Ferguson, 2015;Ferguson et al, 2013;Barton et al, 2016;Flynn et al, 2017;Louie et al, 2018;Quadeer et al, 2019aQuadeer et al, , 2020 and for determining networks of residues important for mediating protein structure and function (Dahirel et al, 2011;Quadeer et al, 2014Quadeer et al, , 2018Ahmed et al, 2019;Gaiha et al, 2019). However, residue-residue interactions, represented in the maximum entropy fitness landscape model by the coupling parameters (Equation 3 in STAR Methods), seem to be especially important for HCV E2 1b.…”