Poster Presentation International Peptide Symposium 2023

Protein tryptophan modification enabled by using S-protected cysteine sulfoxide under mild acid conditions (#276)

Daishiro Kobayashi 1 , Junya Hayashi 1 , Kota Hidaka 1 , Kento Ohkawachi 1 , Yutaka Komura 1 , Masaya Denda 1 , Akira Otaka 1
  1. Tokushima University, Tokushima, NOT US OR CANADA, Japan

Chemical modifications of specific amino acids on proteins have paved the way for improvement of their chemical or pharmacological properties, thereby promoting the development of protein-based drugs. Among all proteinogenic residues, tryptophan (Trp) is considered an ideal residue selectively modified due to its less abundant exposure feature. Thus, the methodology allowing for Trp-targeting modification has been in demand for novel protein biologics. Recently, our group developed an Trp-selective modification reaction using S-methoxybenzyl cysteine sulfoxide (Cys(MBzl)(O) 1) in methansulfonic acid (MSA)−trifluoroacetic acid (TFA)ref.1, which proceeds via formation of S-chlorocysteine (S-Cl Cys 2) accompanying the leaving of MBzl cation to generate Cys-Trp linkage (4) through SEAr reaction. The formation of the MBzl cation requires highly acidic conditions (MSA/TFA system), which, however, causes protein denaturation.

In this context, we explored the protein-friendly Trp-modification protocol by a cysteine sulfoxide with the combination of the sulfoxides and reaction conditions varying. Consequently, we found that S-acetamidomethyl (Acm) cysteine sulfoxide (Cys(Acm)(O): 5) serves as a suitable sulfenylating agent working under mild acid conditions (0.1% TFA in AcOH) in the presence of MgCl2. Additionally, the application of the developed protocol to proteins will be presented.

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Figure 1. The overview of the developed reaction.

  1. Kobayashi, D.; Kuraoka, E.; Hayashi, J.; Yasuda, T.; Kohmura, Y.; Denda, M; Harada, N.; Inagaki, N. and Otaka, A. (2022) ACS. Med. Chem. Lett. 13, 1125–1130.