Cystine-knot peptides targeting cancer-relevant human cytotoxic T lymphocyte-associated antigen 4 (CTLA-4).

Cystine-knot peptides sharing a common fold but displaying a notably large diversity within the primary structure of flanking loops have shown great potential as scaffolds for the development of therapeutic and diagnostic agents. In this study, we demonstrated that the cystine-knot peptide MCoTI-II, a trypsin inhibitor from Momordica cochinchinensis, can be engineered to bind to cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), an inhibitory receptor expressed by T lymphocytes, that has emerged as a target for the treatment of metastatic melanoma. Directed evolution was used to convert a cystine-knot trypsin inhibitor into a CTLA-4 binder by screening a library of variants using yeast surface display.

Fragmentation follows structure: top-down mass spectrometry elucidates the topology of engineered cystine-knot miniproteins.

Over the last decades the field of pharmaceutically relevant peptides has enormously expanded. Among them, several peptide families exist that contain three or more disulfide bonds. In this context, elucidation of the disulfide patterns is extremely important as these motifs are often prerequisites for folding, stability, and activity.

Combinatorial optimization of cystine-knot peptides towards high-affinity inhibitors of human matriptase-1.

Cystine-knot miniproteins define a class of bioactive molecules with several thousand natural members. Their eponymous motif comprises a rigid structured core formed by six disulfide-connected cysteine residues, which accounts for its exceptional stability towards thermic or proteolytic degradation. Since they display a remarkable sequence tolerance within their disulfide-connected loops, these molecules are considered promising frameworks for peptide-based pharmaceuticals.

Structural characterization of Spinacia oleracea trypsin inhibitor III (SOTI-III).

In recent decades, several canonical serine protease inhibitor families have been classified and characterized. In contrast to most trypsin inhibitors, those from garden four o'clock (Mirabilis jalapa) and spinach (Spinacia oleracea) do not share sequence similarity and have been proposed to form the new Mirabilis serine protease inhibitor family. These 30-40-amino-acid inhibitors possess a defined disulfide-bridge topology and belong to the cystine-knot miniproteins (knottins).

Oxidative folding of peptides with cystine-knot architectures: kinetic studies and optimization of folding conditions.

Bioactive peptides often contain several disulfide bonds that provide the main contribution to conformational rigidity and structural, thermal, or biological stability. Among them, cystine-knot peptides-commonly named "knottins"-make up a subclass with several thousand natural members. Hence, they are considered promising frameworks for peptide-based pharmaceuticals.

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.

From pico to nano: biofunctionalization of cube-octameric silsesquioxanes by peptides and miniproteins.

Polyhedral silsesquioxanes are considered valuable conjugation scaffolds. Nevertheless, only a few examples of silsesquioxane-assembled peptide oligomers have been reported to date. We developed a new bioorthogonal cube-octameric silsesquioxane (COSS) scaffold bearing eight aminooxy coupling sites allowing for the conjugation of diverse peptides via oxime ligation.