CONTROL OF PROTEIN-LIGAND RECOGNITION USING A STIMULI-RESPONSIVE POLYMER

STIMULI-responsive polymers exhibit reversible phase changes in respon se to changes in environmental factors such as pH or temperature(1-14) . Conjugating such polymers to antibodies and proteins provides molecu lar systems for applications such as affinity separations, immunoassay s and enzyme recovery and recycling(15-25). Here we show that conjugat ing a temperature-sensitive polymer to a genetically engineered site o n a protein allows the protein's ligand binding affinity to be control led. We synthesized a mutant of the protein streptavidin to enable sit e-specific conjugation of the responsive polymer near the protein's bi nding site. Normal binding of biotin to the modified protein occurs be low 32 degrees C, whereas above this temperature the polymer collapses and blocks binding. The collapse of the polymer and thus the enabling and disabling of binding, is reversible. Such environmentally trigger ed control of binding may find many applications in biotechnology and biomedicine, such as the control of enzyme reaction rates and of biose nsor activity, and the controlled release of drugs.