Fig. 4: Molecular modeling of modified SpyCatcher mutants.

A–H Snapshots of the indicated mutant models following 10 ns simulations at 300 K, displayed as blue ribbon cartoons with side chain conformations shown only for the modified residue (cyan) and key catalytic residues Glu77 and Lys31 (blue). For each mutant, the SpyCatcher-SpyTag structure (PDB 4MLI) is superimposed in green with the SpyTag strand highlighted (red). Models with steric clashes between the biotin modification and SpyTag are labeled in cyan, models without steric clashes in blue. Red Arrow in C points to SpyCatcher strand E where the catalytic Glu77 is displaced.