Kinetics control preferential heterodimer formation of platelet-derived growth factor from unfolded A- and B-chains

Synthetic Cystine-Knot Miniproteins - Valuable Scaffolds for Polypeptide Engineering

Peptides with the cystine-knot architecture, often termed knottins, are promising scaffolds for biomolecular engineering. These unique molecules combine diverse bioactivities with excellent structural, thermal, and proteolytical stability. Being different in the composition and structure of their amino acid backbone, knottins share the same core element, namely cystine knot, which is built by six cysteine residues forming three disulfides upon oxidative folding. This motif ensures a notably rigid framework that highly tolerates both rational and combinatorial changes in the primary structure. Being accessible through recombinant production and total chemical synthesis, cystine-knot miniproteins can be endowed with novel bioactivities by variation of surface-exposed loops and incorporation of non-natural elements within their non-conserved regions towards the generation of tailor-made peptidic compounds. In this chapter the topology of cystine-knot peptides, their synthesis and applications for diagnostics and therapy is discussed.

Chemical synthesis, backbone cyclization and oxidative folding of cystine-knot peptides: promising scaffolds for applications in drug design

Cystine-knot peptides display exceptional structural, thermal, and biological stability. Their eponymous motif consists of six cysteine residues that form three disulfide bonds, resulting in a notably rigid structural core. Since they highly tolerate either rational or combinatorial changes in their primary structure, cystine knots are considered to be promising frameworks for the development of peptide-based pharmaceuticals. Despite their relatively small size (two to three dozens amino acid residues), the chemical synthesis route is challenging since it involves critical steps such as head-to-tail cyclization and oxidative folding towards the respective bioactive isomer. Herein we describe the topology of cystine-knot peptides, their synthetic availability and briefly discuss potential applications of engineered variants in diagnostics and therapy.