Modulation of single-chain antibody affinity with temperature-responsive elastin-like polypeptide linkers

Single-chain antibodies are genetically engineered constructs composed of a V_H and V_L domain of an antibody linked by a flexible peptide linker, commonly (GGGGS)₃. We asked whether replacement of this flexible linker with peptides known to undergo environmentally induced structural transitions could lead to antibodies with controlled binding and release characteristics. To this end, we genetically modified and produced a series of anti-fluorescein single-chain antibodies with the general linker sequence (VPGXG)_n, where n is 1.2 to 3 and X is Val or His, to evaluate the effects of linker length and composition. Our results indicate that single-chain antibodies containing elastin-like polypeptide linkers have equilibrium affinity (K_D) comparable to wild-type (GGGGS)₃ at room temperature but altered binding kinetics and faster ligand release as the temperature is raised. These results are consistent with the increased molecular order and contraction that elastin-like polypeptides are known to undergo with increased temperature. Modulation of antibody affinity using stimulus-responsive linkers may have applications in biosensors, drug delivery, and bioseparations.