A minimalist peptide ligand for IgG by minimizing the binding domain of protein A

Abstract

Large scale application of antibody related drug has been promoting the development of short ligand with low cost and high stability for affinity chromatographic purification of immunoglobulin G (IgG). This study presents a strategy to design a short peptide ligand by minimizing the IgG binding portion from a commercial ligand of Protein A. A short hexapeptide (FYEILH) was thus screened out by the real screening technique of STD-NMR. It presented a comparable binding activity to Protein A, with the dissociation constant (Kd) of 1.8 × 10−6 mol/L, the static binding capacity of 49.7 mg/mL, and the purity of 94% for hIgG from chromatographic purification of serum feedstock in a single step. Epitope mapping analysis by STD-NMR indicated that the carboxy groups of the charged residue E (glutamic acid) in FYEILH was the most adjacent part in binding with hIgG molecule and thus the electronic interactions among them was the dominating binding mechanism. Such mechanism was a little different from Protein A and consequently leaded to its much milder chromatographic conditions of loading at pH 6.0 and eluting at 0.5 mol/L NaCl. The study provided a strategy of reducing larger binding domains of huge Protein A molecule to smaller functional peptide ligand, and offered a potential alternative ligand with low synthesis cost for IgG purification.