Electrochemical Triggering of Reflectin Protein Assembly

Abstract

In this work, we demonstrate electrochemical triggering and assembly of reflectin, the protein that mediates neuronal fine-tuning of color reflected from skin cells used for camouflage and communication in squids. Electrochemical reduction of histidine residues in the protein acts as an in vitro surrogate for phosphorylation in vivo, driving the assembly previously shown to regulate its function. Using micro-drop voltammetry and in situ dynamic light scattering, we demonstrate selective reduction of the imidazolium sidechains of histidine in monomers, oligopeptides and reflectin in acidic solution. The formal reduction potential of imidazolium proves readily distinguishable from those of hydronium and primary amines, allowing unequivocal confirmation of the direct and energetically-selective deprotonation of histidine in reflectin. The resulting “electro-assembly” methodology provides a new approach to probe, understand, and control the mechanisms that dynamically tune protein structure and function. Figure 1