Tailor-made designer helical peptides that induce mitochondrion-mediated cell death without necrosis

Bcl-XL-binding helical peptides possessing d-Ala residues at their C-termini with the advantage of long-lasting intracellular stabilities

We attached d-Ala residues to cross-linked helical peptides based on the pro-apoptotic protein Bad at their C-termini. The d-Ala attachment had little influence on the secondary structures and binding abilities against Bcl-X_L. The d-Ala attached helical peptides were much more stable in cells than original ones and efficiently induced apoptosis of the cells.

Hydrocarbon constrained peptides - understanding preorganisation and binding affinity

The development of constrained peptides represents an emerging strategy to generate peptide based probes and hits for drug-discovery that address challenging protein-protein interactions (PPIs). In this manuscript we report on the use of a novel α-alkenylglycine derived amino acid to synthesise hydrocarbon constrained BH3-family sequences (BIM and BID). Our biophysical and structural analyses illustrate that whilst the introduction of the constraint increases the population of the bioactive α-helical conformation of the peptide in solution, it does not enhance the inhibitory potency against pro-apoptotic Bcl-x_L and Mcl-1 PPIs. SPR analyses indicate binding occurs via an induced fit mechanism whilst X-ray analyses illustrate none of the key interactions between the helix and protein are disturbed. The behaviour derives from enthalpy-entropy compensation which may be considered in terms of the ground state energies of the unbound constrained and unconstrained peptides; this has implications for the design of preorganised peptides to target protein-protein interactions.