Inducible, Selective Labeling of Proteins via Enzymatic Oxidation of Tyrosine

Chemical modification of proteins - challenges and trends at the start of the 2020s

Ribosomally expressed proteins perform multiple, versatile, and specialized tasks throughout Nature. In modern times, chemically modified proteins, including improved hormones, enzymes, and antibody-drug-conjugates have become available and have found advanced industrial and pharmaceutical applications. Chemical modification of proteins is used to introduce new functionalities, improve stability or drugability. Undertaking chemical reactions with proteins without compromising their native function is still a core challenge as proteins are large conformation dependent multifunctional molecules. Methods for functionalization ideally should be chemo-selective, site-selective, and undertaken under biocompatible conditions in aqueous buffer to prevent denaturation of the protein. Here the present challenges in the field are discussed and methods for modification of the 20 encoded amino acids as well as the N-/C-termini and protein backbone are presented. For each amino acid, common and traditional modification methods are presented first, followed by more recent ones.

Non-Genetic Generation of Antibody Conjugates Based on Chemoenzymatic Tyrosine Click Chemistry

The availability of tools to generate homogeneous and stable antibody conjugates without recombinant DNA technology is a valuable asset in fields spanning from in vitro diagnostics to in vivo imaging and therapeutics. We present here a general approach for the conjugation to human IgG1 antibodies, by employing a straightforward two-stage protocol based on antibody deglycosylation followed by tyrosinase-mediated ortho-quinone strain-promoted click chemistry. The technology is validated by the efficient and clean generation of highly potent DAR2 and DAR4 antibody-drug conjugates (ADCs) with cytotoxic payloads MMAE or PBD dimer, and their in vitro evaluation.

Highly Efficient Mono-Functionalization of Knob-in-Hole Antibodies with Strain-Promoted Click Chemistry

Knob-in-hole antibodies can be utilized to introduce a single tag for chemo-enzymatic functionalization. By either introducing a single C-terminal sortase tag (sortase-tag expressed protein ligation) or tyrosine tag (G4Y), mono-functionalization of the monoclonal antibody trastuzumab was achieved rapidly and in high yields. This method was applied to selectively and efficiently introduce a single fluorescent tag, cytokine or single-chain variable fragment, as well as produce clean homo dimers of trastuzumab.