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Moazzam A, Stanojlovic V, Hinterholzer A, Holzner C, Roschger C, Zierer A, Wiederstein M, Schubert M, Cabrele C. Backbone distortions in lactam-bridged helical peptides. J Pept Sci 2022; 28:e3400. [PMID: 34984761 PMCID: PMC9285742 DOI: 10.1002/psc.3400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 12/14/2021] [Accepted: 12/14/2021] [Indexed: 11/11/2022]
Abstract
Side‐chain‐to‐side‐chain cyclization is frequently used to stabilize the α‐helical conformation of short peptides. In a previous study, we incorporated a lactam bridge between the side chains of Lys‐i and Asp‐i+4 in the nonapeptide 1Y, cyclo‐(2,6)‐(Ac‐VKRLQDLQY‐NH2), an artificial ligand of the inhibitor of DNA binding and cell differentiation (ID) protein with antiproliferative activity on cancer cells. Herein, we show that only the cyclized five‐residue segment adopts a helical turn whereas the C‐terminal residues remain flexible. Moreover, we present nine 1Y analogs arising from different combinations of hydrophobic residues (leucine, isoleucine, norleucine, valine, and tyrosine) at positions 1, 4, 7, and 9. All cyclopeptides except one build a lactam‐bridged helical turn; however, residue‐4 reveals less helix character than the neighboring Arg‐3 and Gln‐5, especially with residue‐4 being isoleucine, valine, and tyrosine. Surprisingly, only two cyclopeptides exhibit helix propagation until the C‐terminus, whereas the others share a remarkable outward tilting of the backbone carbonyl of the lactam‐bridged Asp‐6 (>40° deviation from the orientation parallel to the helix axis), which prevents the formation of the H‐bond between Arg‐3 CO and residue‐7 NH: As a result, the propagation of the helix beyond the lactam‐bridged sequence becomes unfavorable. We conclude that, depending on the amino‐acid sequence, the lactam bridge between Lys‐i and Asp‐i+4 can stabilize a helical turn but deviations from the ideal helix geometry are possible: Indeed, besides the outward tilting of the backbone carbonyls, the residues per turn increased from 3.6 (typical of a regular α‐helix) to 4.2, suggesting a partial helix unwinding.
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Affiliation(s)
- Ali Moazzam
- Department of Biosciences, Paris Lodron University of Salzburg, Salzburg, Austria.,Current address: School of Chemistry, College of Science, University of Tehran, Tehran
| | - Vesna Stanojlovic
- Department of Biosciences, Paris Lodron University of Salzburg, Salzburg, Austria
| | - Arthur Hinterholzer
- Department of Biosciences, Paris Lodron University of Salzburg, Salzburg, Austria
| | - Christoph Holzner
- Department of Biosciences, Paris Lodron University of Salzburg, Salzburg, Austria
| | - Cornelia Roschger
- Department for Cardiac-, Vascular- and Thoracic Surgery, Johannes Kepler University Linz and Kepler University Hospital GmbH, Linz, Austria
| | - Andreas Zierer
- Department for Cardiac-, Vascular- and Thoracic Surgery, Johannes Kepler University Linz and Kepler University Hospital GmbH, Linz, Austria
| | - Markus Wiederstein
- Department of Biosciences, Paris Lodron University of Salzburg, Salzburg, Austria
| | - Mario Schubert
- Department of Biosciences, Paris Lodron University of Salzburg, Salzburg, Austria
| | - Chiara Cabrele
- Department of Biosciences, Paris Lodron University of Salzburg, Salzburg, Austria
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Roschger C, Neukirchen S, Elsässer B, Schubert M, Maeding N, Verwanger T, Krammer B, Cabrele C. Targeting of a Helix-Loop-Helix Transcriptional Regulator by a Short Helical Peptide. ChemMedChem 2017; 12:1497-1503. [DOI: 10.1002/cmdc.201700305] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 07/17/2017] [Indexed: 12/16/2022]
Affiliation(s)
- Cornelia Roschger
- Department of Molecular Biology; University of Salzburg; Billrothstrasse 11 5020 Salzburg Austria
| | - Saskia Neukirchen
- Department of Molecular Biology; University of Salzburg; Billrothstrasse 11 5020 Salzburg Austria
- Department of Chemistry and Biochemistry; Ruhr-University Bochum; Universitaetsstrasse 150 44801 Bochum Germany
| | - Brigitta Elsässer
- Department of Molecular Biology; University of Salzburg; Billrothstrasse 11 5020 Salzburg Austria
| | - Mario Schubert
- Department of Molecular Biology; University of Salzburg; Billrothstrasse 11 5020 Salzburg Austria
| | - Nicole Maeding
- Department of Molecular Biology; University of Salzburg; Hellbrunnerstrasse 34 5020 Salzburg Austria
| | - Thomas Verwanger
- Department of Molecular Biology; University of Salzburg; Hellbrunnerstrasse 34 5020 Salzburg Austria
| | - Barbara Krammer
- Department of Molecular Biology; University of Salzburg; Hellbrunnerstrasse 34 5020 Salzburg Austria
| | - Chiara Cabrele
- Department of Molecular Biology; University of Salzburg; Billrothstrasse 11 5020 Salzburg Austria
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