Semi-synthesis of a tag-free O-GlcNAcylated tau protein by sequential chemoselective ligation

• Published in: Journal of peptide science Vol. 22; no. 5; pp. 327 - 333
• Main Authors: Schwagerus, Sergej, Reimann, Oliver, Despres, Clement, Smet-Nocca, Caroline, Hackenberger, Christian P. R.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01-05-2016; Wiley Subscription Services, Inc; Wiley
• Subjects: Acetylglucosamine - chemistry; Alzheimer Disease - metabolism; Biochemistry; Biochemistry, Molecular Biology; Chemistry Techniques, Synthetic; Humans; Life Sciences; Molecular Structure; native chemical ligation; O-GIcNac; Peptides; Peptides - chemistry; Protein Processing, Post-Translational; protein synthesis; Serine - chemistry; tag-free purification; tau protein; tau Proteins - chemical synthesis; tau Proteins - chemistry; protein synthesis; tag-free purification; native chemical ligation; O-GIcNac; tau protein
• ISSN: 1075-2617; 1099-1387
• DOI: 10.1002/psc.2870

In this paper, the first semi‐synthesis of the Alzheimer‐relevant tau protein carrying an O‐GlcNAcylation is demonstrated by using sequential chemoselective ligation. The 52‐amino acid C‐terminus of tau was obtained by native chemical ligation between two synthetic peptide fragments, one carrying the O‐GlcNAc moiety on Ser400, which has recently been demonstrated to inhibit tau phosphorylation and to hinder tau oligomerization, and the other equipped with a photocleavable biotin handle. After desulfurization to deliver a native alanine at the ligation junction, the N‐terminal cysteine was unmasked, and the peptide was further used for expressed protein ligation to generate the full‐length tau protein, which was purified by a photocleavable biotin tag. We thus provide a synthetic route to obtain a homogenous tag‐free O‐GlcNAcylated tau protein that can further help to elucidate the significance of posttranslational modification on the tau protein and pave the way for evaluating possible drug targets in Alzheimer's disease. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.
We present the first semi‐synthesis of the full‐length tau protein carrying an O‐GlcNAc moiety at S400, a site shown to inhibit tau phosphorylation at neighboring serine residues. Native chemical ligation was combined with expressed protein ligation to obtain the desired homogeneously modified tau protein. Pure protein was finally obtained by means of a photocleavable biotin tag.