A photo-responsive protein-polymer bioconjugate for control of a model protein

Stimuli-responsive bioconjugates have been investigated as a means of controlling protein behavior through conjugation of a responsive polymer to a protein. These bioconjugates have been used in many applications including purification and recovery of proteins, biosensing, and control over protein oligomer formation. We have prepared stimuli-responsive bioconjugates to provide spatiotemporal control over enzymatic activity through a covalently linked photo-responsive copolymer. Photo-responsiveness was conferred through an azobenzene-containing monomer which undergoes a light-induced cis-trans isomerization. Controlled radical polymerization was used to create a panel of polymers of varying size and azobenzene monomer content which was assayed for its ability to allow photo-control using a model protein, alkaline phosphatase (phoA). Site-specific bioconjugation of these photo-responsive polymers was achieved through introduction of a cysteine residue to wild-type phoA which reacted with the maleimide-functionalized responsive polymer. In addition to screening the influence of polymer size and composition, several conjugation sites on the protein were tested to probe the effect of distance to the active site on photo-responsivity.