Peptide segment ligation strategy without use of protecting groups.
We describe the concept and the verification of a chemical ligation approach to the synthesis of proteins using peptide segments with no protecting groups and no activation of the C-terminal alpha-carboxyl group. This approach consists of three steps: (i) aldehyde introduction, in which a masked glycolaldehyde ester is linked to the carboxyl terminus of an unprotected peptide by reverse proteolysis; (ii) ring formation, in which the unmasked aldehyde reacts with the N-terminal alpha-amino group of the second unprotected peptide containing either a cysteine or a threonine residue to form a thiazolidine or oxazolidine ring at an acidic pH; and (iii) rearrangement in which O-acyl ester linkage is transferred to N-acyl amide linkage to form a peptide bond with a pseudoproline structure at higher pH. The feasibility of this scheme was verified by a model study on small compounds and its potential was demonstrated by the synthesis of a 50-residue epidermal growth factor-like peptide containing a preformed disulfide bond.
Department of Microbiology and Immunology, Vanderbilt University, Nashville, TN 37232-2363.
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D000595:Amino Acid Sequence; D003545:Cysteine; D004220:Disulfides; D004815:Epidermal Growth Factor / Q000138:chemical synthesis*; D004952:Esters; D007202:Indicators and Reagents; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry; D011506:Proteins / Q000138:chemical synthesis* / Q000737:chemistry; D013912:Threonine
D004220:Disulfides; D004952:Esters; D007202:Indicators and Reagents; D010455:Peptides; D011506:Proteins; D013912:Threonine; D004815:Epidermal Growth Factor; D003545:Cysteine