Rapid Cross-Metathesis for Reversible Protein Modifications via Chemical Access to Se-Allyl-selenocysteine in Proteins

Abstract

Cross-metathesis (CM) has recently emerged as a viable strategy for protein modification. Here, efficient protein CM has been demonstrated through biomimetic chemical access to Se-allyl-selenocysteine (Seac), a metathesis-reactive amino acid substrate, via dehydroalanine. On-protein reaction kinetics reveal a rapid reaction with rate constants of Seac-mediated-CM comparable or superior to off-protein rates of many current bioconjugations. This use of Se-relayed Seac CM on proteins has now enabled reactions with substrates (allyl GlcNAc, N-allyl acetamide) that were previously not possible for the corresponding sulfur analogue. This CM strategy was applied to histone proteins to install a mimic of acetylated lysine (KAc, an epigenetic marker). The resulting synthetic H3 was successfully recognized by antibody that binds natural H3-K9Ac. Moreover, Cope-type selenoxide elimination allowed this putative marker (and function) to be chemically expunged, regenerating an H3 that can be rewritten to complete a chemically enabled “write (CM)–erase (ox)–rewrite (CM)” cycle.

Selective chemical protein modification

“…Determination of sensitivity to accessibility, self-metathesis and reagent reactivity has delineated predictive rules for this protein reaction 134 . Moreover, tuning of heteroatom (S-Se) in Se-allylselenocysteine led to a significant increase in reaction rate and expanded substrate scope 135 ; this was applied to a chemically controlled 'write-read-erase' histone protein modification cycle.…”

“…131 These reactions typically (but not always) proceed with low substrate control in their diastereoselection and so a mixture of D/L-epimers is produced at the site of modification. Dha also provides a viable method for chemically creating selenocysteines in proteins 135 . Although only shown for a single example (Se-allyl cysteine), the discovery of conditions for creating suitable Se nucleophiles for this addition may enable broader methods.…”

Recent Advancements in Stereoselective Olefin Metathesis Using Ruthenium Catalysts

“…Z-selective ethenolysis can also be employed to form macrocyclic peptides with high E-content (Table 21) [161]. Biological applications are a developing area for OM because of the ability to incorporate amino acids with pendant olefins into peptides and proteins [155][156][157][158][159]. Unfortunately, controlling olefin geometry in amino acid containing products has been difficult.…”

From Chemical Mutagenesis to Post‐Expression Mutagenesis: A 50 Year Odyssey

“…reduction) to exploit the same disconnection. Although efficient cross‐metathesis on proteins has, to date, exploited chalcogen‐mediated relay effects17, 46 (and hence access to longer side chains), multiply relayed methods could be envisaged, for example, for the C β −C γ disconnection (B).…”