Reversible chemoselective tagging and functionalization of methionine containing peptides

Abstract

Reagents were developed to allow chemoselective tagging of methionine residues in peptides and polypeptides, subsequent bioorthogonal functionalization of the tags, and cleavage of the tags when desired. This methodology can be used for triggered release of therapeutic peptides, or release of tagged protein digests from affinity columns.

Functional Modification of Thioether Groups in Peptides, Polypeptides, and Proteins

“…Follow up studies by Deming and coworkers described the reversible modification of thioether groups in polypeptides via the chemoselective dealkylation of select methionine sulfonium residues ( Figure 9). 62 A series of studies were used to identify alkyl substituents on Met sulfoniums that were more prone to nucleophilic attack. While simple alkyl (e.g.…”

“…Using these insights, functional benzylic halides were designed for reaction with Met residues to give stable sulfonium products, allow secondary modifications, and then allow selective "tag" removal by addition of a nucleophile under mild conditions. 62 Such tags may be used for attachment of probes for imaging, for selective purification or detection in complex mixtures, for enhancement of 20 therapeutic properties, or as labels to assist in proteomic analysis ( Figure 9). These Met alkylation and dealkylation reactions were found to be compatible with deprotection of other functional groups, and use a natural amino acid that is readily incorporated into peptide, protein or polymer sequences, enhancing the utility of this methodology.…”

Multimodal Switching of Conformation and Solubility in Homocysteine Derived Polypeptides

“…After removal of protecting groups, water soluble, α-helical 5 was obtained with reproducible and precisely controlled chain lengths up to over 300 residues long. To study the ability of 5 to respond to stimuli, samples were subjected to either chemical alkylation 12 or mild oxidation 11 (Scheme 1). Unmodified 5 gave a CD spectrum with characteristic minima at 208 and 222 nm indicating a greater than 95% α-helical conformation in DI water at 20 ºC ( Figure 2B).…”

Use of Methionine Alkylation to Prepare Cationic and Zwitterionic Block Copolypeptide Vesicles

“…These "M click" functionalizations are compatible with deprotection of other functional groups, use an inexpensive, natural amino acid, and allow the introduction of a diverse range of functional and reactive groups onto polypeptides. [3,8] Here, we have demonstrated the utility of M alkylation chemistry for the facile preparation of model amphiphilic block copolypeptides that can form vesicle assemblies in water (Scheme 1).…”

“…Our lab recently reported the use of M alkylation as a facile means to reversibly or irreversibly introduce useful functionality and chemically reactive groups onto polypeptides. [3,8] This work originated from pioneering studies of M alkylation in proteins, which were mainly focused on use of nonfunctional alkylating reagents to probe inhibition of enzyme active sites. [9][10][11] We have found that M residues can undergo chemoselective, broad scope, highly efficient alkylation reactions in homo-and copolypeptides yielding stable sulfonium derivatives.…”