Incorporation of cis - and trans -4,5-Difluoromethanoprolines into Polypeptides (original) (raw)

4-Fluoroproline derivative peptides: effect on PPII conformation and SH3 affinity

Journal of Peptide Science, 2006

Eukaryotic signal transduction involves the assembly of transient protein–protein complexes mediated by modular interaction domains. Specific Pro-rich sequences with the consensus core motif PxxP adopt the PPII helix conformation upon binding to SH3 domains. For short Pro-rich peptides, little or no ordered secondary structure is usually observed before binding interactions. The association of a Pro-rich peptide with the SH3 domain involves unfavorable binding entropy due to the loss of rotational freedom on forming the PPII helix. With the aim of stabilizing the PPII helix conformation in the Pro-rich HPK1 decapeptide PPPLPPKPKF (P2), a series of P2 analogues was prepared, in which specific Pro positions were alternatively occupied by 4(S)- or 4(R)-4-fluoro-L-proline. The interactions of these peptides with the SH3 domain of the HPK1-binding partner HS1 were quantitatively analyzed by the NILIA-CD approach. A CD thermal analysis of the P2 analogues was performed to assess their propensity to adopt the PPII helix conformation. Contrary to our expectations, the Kd values of the analogues were lower than that of the parent peptide P2. These results clearly show that the induction of a stable PPII helix conformation in short Pro-rich peptides is not sufficient to increase their affinity toward the SH3 domain and that the effect of 4-fluoroproline strongly depends on the position of this residue in the sequence and the chirality of the substituent in the pyrrolidine ring. Copyright © 2006 European Peptide Society and John Wiley & Sons, Ltd.

Modulating Protein Structure with Fluorous Amino Acids: Increased Stability and Native-like Structure Conferred on a 4-Helix Bundle Protein by Hexafluoroleucine

Journal of the American Chemical Society, 2006

There has recently been much interest in exploiting the unusual properties associated with fluorocarbons to modulate the physicochemical properties of proteins. Here we present a detailed investigation into the effect on structure and stability of systematically repacking the hydrophobic core of a model protein with the extensively fluorinated (fluorous) amino acid L-5,5,5,5′,5′,5′-hexafluoroleucine (hFLeu). The starting point was a 27-residue peptide, R4-H, that adopts an antiparallel 4-R-helix bundle structure, and in which the hydrophobic core comprises six layers of leucine residues introduced at the "a" and "d" positions of the canonical heptad repeat. A series of peptides were synthesized in which the central two (R 4-F2), four (R4-F4), or all six layers (R4-F6) of the core were substituted hFLeu. The free energy of unfolding increases by 0.3 (kcal/mol)/hFLeu on repacking the central two layers and by an additional 0.12 (kcal/mol)/hFLeu on repacking additional layers, so that R 4-F6 is ∼ 25% more stable than the nonfluorinated protein R4-H. One-dimensional proton, two-dimensional 1 H-15 N HSQC, and 19 F NMR spectroscopies were used to examine the effect of fluorination on the conformational dynamics of the peptide. Unexpectedly, increasing the degree of fluorination also appears to result in peptides that possess a more structured backbone and less fluid hydrophobic core. The latter only occurs in R 4-F4 and R4-F6, suggesting that crowding of the hFLeu residues may restrict the amplitude and/or time scales for rotation of the side chains.

The use of 4,4,4-trifluorothreonine to stabilize extended peptide structures and mimic β-strands

Beilstein journal of organic chemistry, 2017

Pentapeptides having the sequence R-HN-Ala-Val--Val-Leu-OMe, where the central residue is L-serine, L-threonine, (2,3)-L-CF-threonine and (2,3)-L-CF-threonine were prepared. The capacity of (2,3)- and (2,3)-CF-threonine analogues to stabilize an extended structure when introduced in the central position of pentapeptides is demonstrated by NMR conformational studies and molecular dynamics simulations. CF-threonine containing pentapeptides are more prone to mimic β-strands than their natural Ser and Thr pentapeptide analogues. The proof of concept that these fluorinated β-strand mimics are able to disrupt protein-protein interactions involving β-sheet structures is provided. The CF-threonine containing pentapeptides interact with the amyloid peptide Aβ in order to reduce the protein-protein interactions mediating its aggregation process.