Chemical Modification of the N Termini of Unprotected Peptides for Semisynthesis of Modified Proteins by Utilizing a Hydrophilic Protecting Group |
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| Authors: | Dr Chaitra Chandrashekar Prof Dr Ryo Okamoto Prof Dr Masayuki Izumi Prof Dr Yasuhiro Kajihara |
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| Institution: | Department of Chemistry and Project Research Center for, Fundamental Sciences, Graduate School of Science, Osaka University1-1, Toyonaka, Osaka, 5600043 Japan |
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| Abstract: | A simple and efficient strategy for the selective modification of the peptide N terminus with an unnatural amino acid is described. A peptide having a SUMO-HisTag-TEV sequence (SUMO: small ubiquitin-related modifier, TEV: tobacco etch virus) preceding the N terminus of the target peptide was designed. Recombinant expression in E. coli and subsequent SUMO protease cleavage yielded the HisTag-TEV-target peptide. Partial protection of the lysine side chains of this peptide with d -glucopyranosyloxycarbonyl and removal of the HisTag-TEV sequence by TEV protease yielded the partially protected peptide with a free N-terminal amine. Coupling of selenocysteine selectively at the N terminus and subsequent acidic deprotection of the carbohydrate protecting groups yielded a modified peptide that can be used for native chemical ligation (NCL). As a proof of concept, the modification of a longer recombinant peptide with selenocysteinylserine (GalNAc) at the N terminus was demonstrated. |
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| Keywords: | peptides protecting groups native chemical ligation selenocysteine semisynthesis |
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