title: Synthesis and conformation of an analog of the helix-loop-helix domain of the Id1 protein containing the O-acyl iso-prolyl-seryl switch motif.
abstract: Synthetic peptides reproducing the helix-loop-helix (HLH) domains of the Id proteins fold into highly stable helix bundles upon self-association. Recently, we have shown that the replacement of the dipeptide Val-Ser at the loop-helix-2 junction with the corresponding O-acyl iso-dipeptide leads to a completely unfolded state that only refolds after intramolecular O --> N acyl migration. Herein, we report on an Id HLH analog based on the substitution of the Pro-Ser motif at the helix-1-loop junction with the corresponding O-acyl iso-dipeptide. This analog has been successfully synthesized by solid-phase Fmoc chemistry upon suppression of DKP formation. No secondary structure could be detected for the O-acyl iso-peptide before its conversion into the native form by O --> N acyl shift. These results show that the loop-helix junctions are determinant for the folded/unfolded state of the Id HLH domain. Further, despite the high risk of DKP formation, peptides containing O-acyl iso-Pro-Ser/Thr units are synthetically accessible by Fmoc chemistry.
authors.affiliation: Fakultät für Chemie und Biochemie, Ruhr-Universität Bochum, Bochum, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Beisswenger
authors.forename: Taku
authors.initials: T
authors.lastname: Yoshiya
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Kiso
authors.forename: Chiara
authors.initials: C
authors.lastname: Cabrele
mesh_terms: D000595:Amino Acid Sequence; D018257:Helix-Loop-Helix Motifs; D006801:Humans; D051798:Inhibitor of Differentiation Protein 1 / Q000737:chemistry* / Q000235:genetics*; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry* / Q000235:genetics; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
chemical_list: D051798:Inhibitor of Differentiation Protein 1; D010455:Peptides