Development of a High‐Affinity Antibody‐Binding Peptide for Site‐Specific Modification

Abstract

Immunoglobulin G (IgG)‐binding peptides such as 15‐IgBP are convenient tools for the site‐specific modification of antibodies and the preparation of homogeneous antibody–drug conjugates. A peptide such as 15‐IgBP can be selectively crosslinked to the fragment crystallizable region of human IgG in an affinity‐dependent manner via the ϵ‐amino group of Lys8. Previously, we found that the peptide 15‐Lys8Leu has a high affinity (Kd=8.19 nM) due to the presence of the γ‐dimethyl group in Leu8. The primary amino group required for the crosslinking to the antibodies has, however, been lost. Here, we report the design and synthesis of a novel unnatural amino acid, 4‐(2‐aminoethylcarbamoyl)leucine (Aecl), which possesses both the γ‐dimethyl fragment and a primary amino group. A peptide containing Aecl8 (15‐Lys8Aecl) was synthesized and showed a binding affinity ten times higher (Kd=24.3 nM) than that of 15‐IgBP (Kd=267 nM). Fluorescein isothiocyanate (FITC)‐labeled 15‐Lys8Aecl with an N‐hydroxy succinimide ester at the side chain of Aecl8 (FITC‐15‐Lys8Aecl(OSu)) successfully labeled an antibody (trastuzumab, Herceptin®) with the fluorophore. This peptide scaffold has both strong binding affinity and crosslinking capability, and could be a useful tool for the selective chemical modification of antibodies with molecules of interest such as drugs.

A peptide selectively recognizes Gram-negative bacteria and forms a bacterial extracellular trap (BET) through interfacial self-assembly

“…In order to verify the selective recognition of Gram-negative bacteria by LTPs, LTPs and polymyxin B (PMB) were labeled with fluorescein isothiocyanate (FITC). 42 PMB is a peptide antibiotic reported to have high binding affinity to LPS. 43 Six FITC-labeled LTPs and PMB were co-incubated with Gram-negative Escherichia coli ( E. coli ) or Gram-positive Staphylococcus aureus ( S. aureus ).…”

Synergistic vesicle-vector systems for targeted delivery

“…Additionally, peptides can be adsorbed and/or interpolated onto the liposomal surface via electrostatic and/or hydrophobic interactions [ 45 ]. Furthermore, peptides can be present in several copies simultaneously to achieve a higher binding affinity, and the large specific surface area of nanostructures makes it possible to combine various peptide ligands into a single construct [ 46 ]…”