Figure 2. Protein structure context of natural helicase variants.

Details of PDB structure 1CU1 showing the C-terminal region of the NS3 helicase (amino acid residues 241 – 631). The NS3 protease natural substrate of proteolysis is given as a stick model with residues denoted as P₆-P₅-P₄-P₃-P₂-P₁-P₁’ according to the nomenclature of Schechter and Berger³², in which residues surrounding a cleavage site are designated from the N- to the C-terminus with the scissile bond located between P₁ and P₁’. (A) Residues highlighted in cyan where mutations showed increased replication capacity. (B) Residues highlighted in magenta where mutations showed decreased replication capacity. Phe-loop residues T443 and F444 are highlighted in green.