Stereoretentive Post-Translational Protein Editing

Abstract

Chemical post-translational methods now allow convergent side-chain editing of proteins as a form of direct chemical mutagenesis without needing to resort to genetic intervention. Current approaches that allow the creation of constitutionally native side-chains via C-C formation using off-protein carbon-centred C· radicals added to unnatural amino acid radical acceptor SOMOphile 'tags' such as dehydroalanine are benign and wide-ranging. However, they also typically create epimeric mixtures of D-/L-residues. Here we describe a light-mediated desulfurative method that, through the creation and reaction of stereoretained on-protein L-alanyl Cβ· radicals, allows Cβ-Hγ, Cβ-Oγ, Cβ-Seγ, Cβ-Bγ and Cβ-Cγ bond formation to flexibly generate site-selectively edited proteins with full retention of native stereochemistry under mild conditions from a natural amino acid. This methodology shows great potential to explore protein side-chain diversity and construct useful bioconjugates.

Kinetic Resolution of Epimeric Proteins enables Stereoselective Chemical Mutagenesis

“…A chemical challenge, especially in the context of PTM research, is the requirement for precise, minimally perturbing linkages between the protein and new functional groups. Creative solutions for this problem are Cys alkylation, frequently used to install methyllysine analogs, 39 and recent desulfurative [40][41][42][43] strategies to incorporate useful functional groups such as spin labels, PTMs, and their analogues.…”