Designing macrocyclic disulfide-rich peptides for biotechnological applications

Abstract

Bioactive peptides have potential as drug leads, but turning them into drugs is a challenge because of their typically poor metabolic stability. Molecular grafting is one approach to stabilizing and constraining peptides and involves melding a bioactive peptide sequence onto a suitable molecular scaffold. This method has the benefit of improving the stability of the bioactive peptide lead and potentially expanding its functionality. Here we step through the molecular grafting process and describe its successes and limitations. So far, molecular grafting has been successfully used to improve the stability of peptide drug leads, to enhance conformational rigidity, to facilitate delivery to intracellular targets, and in some cases to increase efficacy in oral administration. Although applications of molecular grafting have focused mainly on therapeutic applications, including those for pain, metabolic disease, and cancer, its potential uses are much broader, and we hope this Perspective will inspire wider applications of this molecular design tool in biotechnology.

A One‐Pot “Triple‐C” Multicyclization Methodology for the Synthesis of Highly Constrained Isomerically Pure Tetracyclic Peptides

“…Highly constrained peptides are abundant in nature and display a wide range of different bioactivities . Cyclotides, a class of natural peptides found in plants, provide an intriguing example of this type of a head‐to‐tail cyclized peptide backbone that is crosslinked with multiple conserved disulfide constraints . Cyclic peptides, in general, and cyclotides, in particular, exhibit strongly improved metabolic stabilities and target affinities compared with their linear counterparts .…”

Development of Relaxin-3 Agonists and Antagonists Based on Grafted Disulfide-Stabilized Scaffolds

“…Stapling has also been shown to facilitate peptide delivery to the brain via the intranasal route (Marwari et al, 2019). Given the success with employing molecular grafting as a drug design approach (Li et al, 2009;Phan et al, 2010;Zhang et al, 2015b;Wang and Craik, 2018), we envisioned that single chain RXFP3 agonists and antagonists with improved stability, and possibly also affinity and efficacy, could alternatively be developed by transferring key residues from the two-chain relaxin-3 onto a stable single chain scaffold with appropriate structure. The RXFP3 binding motif (ArgB8, ArgB12, IleB15, ArgB16, IleB19, and PheB20) is predominantly situated on the solvent exposed side of the α-helix located in the native relaxin-3 B-chain (Rosengren et al, 2006).…”

“…Linear peptides such as the R3 B1-22R antagonist and the relaxin-3 B-chain generally are readily broken down in serum and require redesign to be feasible drug leads. One such redesign concept is "molecular grafting" where essential residues for bioactivity are introduced at topologically equivalent positions of a stable scaffold with appropriate structure, as a way to reduce enzymatic susceptibility of the binding motif (Wang and Craik, 2018). The key binding features of relaxin-3 are centered around the B-chain helix, thus an appropriate grafting scaffold for targeting RXFP3 would have to include a helix of similar length to native relaxin-3.…”

In Silico Design of MDM2‐Targeting Peptides from a Naturally Occurring Constrained Peptide

“…An alternative strategy is grafting the MDM2 binding residues to a constrained miniprotein. It has been shown previously that active epitopes can be grafted onto a molecular scaffold with favorable biopharmaceutical properties to overcome the problems of poor stability . Indeed, Li and co‐workers, who used apamin and scorpion toxins as templates for the design of potent p53‐MDM2 and p53‐MDMX peptide inhibitors, have employed this strategy…”

“…It has been shown previously that active epitopes can be grafted onto am olecular scaffold with favorable biopharmaceutical properties to overcome the problems of poor stability. [14] Indeed, Li and co-workers,w ho used apamin and scorpion toxins as templates for the design of potent p53-MDM2 and p53-MDMX peptide inhibitors, have employed this strategy. [15] Grafting of the MDM2 bindinge pitope( F 19 W 23 L 25 )( Figure 1a) to naturally occurring constrained peptides has had much success but also faced severalc hallenges.…”