title: Truncated and helix-constrained peptides with high affinity and specificity for the cFos coiled-coil of AP-1.
abstract: Protein-based therapeutics feature large interacting surfaces. Protein folding endows structural stability to localised surface epitopes, imparting high affinity and target specificity upon interactions with binding partners. However, short synthetic peptides with sequences corresponding to such protein epitopes are unstructured in water and promiscuously bind to proteins with low affinity and specificity. Here we combine structural stability and target specificity of proteins, with low cost and rapid synthesis of small molecules, towards meeting the significant challenge of binding coiled coil proteins in transcriptional regulation. By iteratively truncating a Jun-based peptide from 37 to 22 residues, strategically incorporating i→i+4 helix-inducing constraints, and positioning unnatural amino acids, we have produced short, water-stable, α-helical peptides that bind cFos. A three-dimensional NMR-derived structure for one peptide (24) confirmed a highly stable α-helix which was resistant to proteolytic degradation in serum. These short structured peptides are entropically pre-organized for binding with high affinity and specificity to cFos, a key component of the oncogenic transcriptional regulator Activator Protein-1 (AP-1). They competitively antagonized the cJun-cFos coiled-coil interaction. Truncating a Jun-based peptide from 37 to 22 residues decreased the binding enthalpy for cJun by ∼9 kcal/mol, but this was compensated by increased conformational entropy (TΔS ≤7.5 kcal/mol). This study demonstrates that rational design of short peptides constrained by α-helical cyclic pentapeptide modules is able to retain parental high helicity, as well as high affinity and specificity for cFos. These are important steps towards small antagonists of the cJun-cFos interaction that mediates gene transcription in cancer and inflammatory diseases.
authors.affiliation: School of Biological Sciences, University of Essex, Colchester, United Kingdom.
authors.forename: Tara
authors.initials: T
authors.lastname: Rao
authors.forename: Gloria
authors.initials: G
authors.lastname: Ruiz-Gómez
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Hill
authors.forename: Huy N
authors.initials: HN
authors.lastname: Hoang
authors.forename: David P
authors.initials: DP
authors.lastname: Fairlie
authors.forename: Jody M
authors.initials: JM
authors.lastname: Mason
mesh_terms: D000595:Amino Acid Sequence; D002151:Calorimetry; D002942:Circular Dichroism; D006801:Humans; D016350:Leucine Zippers; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry* / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D011489:Protein Denaturation; D055503:Protein Multimerization; D055550:Protein Stability; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D016760:Proto-Oncogene Proteins c-fos / Q000737:chemistry / Q000378:metabolism*; D013696:Temperature; D018808:Transcription Factor AP-1 / Q000378:metabolism*
chemical_list: D050505:Mutant Proteins; D010455:Peptides; D016760:Proto-Oncogene Proteins c-fos; D018808:Transcription Factor AP-1
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