Abstract
To mimic a hypothetical pathway for protein evolution, we previously tailored a monomeric protein (cyt cb(562) ) for metal-mediated self-assembly, followed by re-design of the resulting oligomers for enhanced stability and metal-based functions. We show that a single hydrophobic mutation on the cyt cb(562) surface drastically alters the outcome of metal-directed oligomerization to yield a new trimeric architecture, (TriCyt1)(3.) This nascent trimer was redesigned into second and third-generation variants (TriCyt2)(3) and (TriCyt3)(3) with increased structural stability and preorganization for metal coordination. The three TriCyt variants combined furnish a unique platform to 1) provide tunable coupling between protein quaternary structure and metal coordination, 2) enable the construction of metal/pH-switchable protein oligomerization motifs, and 3) generate a robust metal coordination site that can coordinate all mid-to-late first-row transition-metal ions with high affinity.