Recent Progress in Chemical Modification of Proteins

Abstract

Chemical modification of proteins is important for creating a myriad of engineered proteins and for elucidating the function and dynamics of proteins in live cells. A wide variety of chemical protein modification methods have been developed and can be categorized into three classes: (i) modification of proteins using the reactivity of naturally occurring amino acids; (ii) modification by bioorthogonal reactions using unnatural amino acids, most of which can be siteselectively incorporated into proteins-of-interest using genetic codon expansion techniques; and (iii) recognition driven chemical modification, which is the only approach that allows modification of endogenous proteins without any genetic manipulation even under heavily crowded and multi-molecular conditions, as in live cells and organisms. All of these approaches have merits and limitations. In this review, we summarize these approaches and discuss their characteristics with respect to specificity, reaction rate and versatility.

Triazolecarbaldehyde Reagents for One‐Step N‐Terminal Protein Modification

“…Site‐specific modification of peptides and proteins is required for the development of pharmaceutical conjugates, bioimaging and medical diagnostics reagents, and protein‐based materials . Chemical approaches have been important tools for modification of reactive side chains in canonical amino acid residues including Lys, Cys, Tyr, Trp, Arg, and Met . The N terminus is an attractive accessible site for specific chemical modification because it represents a unique, yet ubiquitous position in proteins.…”

Synthetic Strategies for Artificial Lipidation of Functional Proteins

“…The in situ labeling efficiency of the protein increased by increasing the lipid‐fused MRHKGS, but a high concentration of lipid‐fused MRHKGS caused cytotoxicity. MTG‐mediated lipidation of proteins is currently limited to a model protein, although it may prove useful for antibody lipidation as MTG recognition of glutamine 295 in a native antibody or the C‐terminal lysine in a recombinant antibody is now used for antibody–drug conjugation. These properties of MTG‐mediated recognition of native glutamine or lysine in a protein can be advantageous in the case of lipidation of an antibody, but if the MTG‐reactive glutamine in a wild‐type protein involves the active site, the labeling of glutamine by MTG will deactivate the protein.…”

Ligand-directed covalent labelling of a GPCR with a fluorescent tag

“…Upon binding of this conjugate, the linker can undergo a substitution reaction with a nucleophilic amino acid side chain (Lys, Ser, Tyr) close to the binding site, forming a new covalent bond between the fluorophore and protein (Figure 1a) 7 . The reactive groups used thus far for labelling proteins are bulky and not readily accommodated within the binding sites of a GPCR or suffer from slow reactivity 8,9 .…”