Allosterically Activated Protein Self‐Assembly for the Construction of Helical Microfilaments with Tunable Helicity

Protein allostery, a chemical‐to‐mechanical effect that can precisely regulate protein structure, exists in many proteins. Herein, we demonstrate that protein allostery can be used to drive self‐assembly for the construction of tunable protein architectures. Calmodulin (CaM) was chosen as a model allosteric protein. Ca2+‐mediated contraction of CaM to a closed state can activate CaM and its ligand to self‐assemble into a 1D protein helical microfilament. Conversely, relaxation of CaM to the open state can unwind and further dissociate the helical assemblies. Fine regulation of the protein conformation by tuning the external Ca2+ level allows us to obtain various protein helical nanostructures with tunable helicity. This study offers a new approach toward chemomechanically controlled protein self‐assembly. Do the twist: In the presence of Ca2+, the allosteric protein calmodulin adopts a closed conformation that leads to tight binding of its ligand and self‐assembly to form twisted helical microfilaments. Tuning this chemically induced protein conformational change by adjusting the concentration of the allosteric signal Ca2+ gives precisely controlled helical protein self‐assembly with tunable helicity.