Fig. 2: Engineering CI2 to promote fold switching and assembly.
From: Engineering protein assemblies with allosteric control via monomer fold-switching
a The native-fold topology of CI2 highlighting the C-terminal antiparallel β-strand (dark blue), highly conserved residues (red), native backbone hydrogen bonds (black dashed lines), the disulfide bond of trypsin inhibitors (orange), and the domain-swapped segment (medium-shade blue). b Top view of the double hexameric arrangement that CI2 adopts in the crystal lattice (6QIY). c Inter-monomer interactions that stabilize the rings in the crystal. d (Left) side view of the double-ring and stereo view of equivalent monomers from top and bottom rings in the standard structure (6QIY). (Right) as in left for the domain-swapped structure (6QIZ). The omit electron density map contoured at 3.0σ is shown for the I39 to E43 segment (sticks). e Mutations used to engineer CI2: (red) wild-type side chain and (blue) replaced side chain. f Comparison between the wild-type NMR structure (3CI2.PDB, red) and the structure of monomeric CI2eng obtained from experimental chemical shifts and CS-Rosetta (blue). g Equilibrium and h kinetics as a function of chemical denaturant for CI2 (red) and CI2eng (blue).
