Accelerating the Association of the Most Stable Protein-Ligand Complex by More than Two Orders of Magnitude

摘要

The complex between the bacterial type 1 pilus subunit FimG and the peptide corresponding to the N-terminal extension (termed donor strand, Ds) of the partner subunit FimF (DsF) shows the strongest reported noncovalent molecular interaction, with a dissociation constant (K-D) of 1.5 x 10(-20) M. However, the complex only exhibits a slow association rate of 330 M-1 s(-1) that limits technical applications, such as its use in affinity purification. Herein, a structure-based approach was used to design pairs of FimGt (a FimG variant lacking its own N-terminal extension) and DsF variants with enhanced electrostatic surface complementarity. Association of the best mutant FimGt/DsF pairs was accelerated by more than two orders of magnitude, while the dissociation rates and 3D structures of the improved complexes remained essentially unperturbed. A K-D value of 8.8 x 10(-22) M was obtained for the best mutant complex, which is the lowest value reported to date for a protein/ligand complex.