Cyclotide Structure and Function: The Role of Membrane Binding and Permeation.

Area of Science:

• Biochemistry
• Molecular Biology
• Drug Discovery

Background:

• Growing interest in peptides for therapeutic applications.
• Cyclotides, a class of cyclic peptides, offer remarkable stability and sequence engineering potential for drug design.
• Natural cyclotides possess intrinsic biological activities and cell-penetrating capabilities.

Purpose of the Study:

• To review cyclotide structures in relation to their biological activities.
• To elucidate the role of membrane binding in cyclotide function and cell entry.
• To compare membrane binding properties across different cyclotide subfamilies.

Main Methods:

• Literature review of cyclotide research.
• Analysis of structural-activity relationships.
• Comparison of physicochemical properties and bioactivities.

Main Results:

• Cyclotides exhibit ultrastable structures and are amenable to sequence engineering.
• Möbius and bracelet cyclotides possess lipid-binding domains for specific recognition of phosphatidylethanolamine phospholipids.
• Membrane binding is correlated with conserved 3D structures, influencing biological properties and cell penetration.
• Trypsin inhibitor cyclotides lack membrane binding but retain cell entry capabilities, differing in properties and bioactivities.

Conclusions:

• Cyclotide structure, particularly membrane binding, is crucial for their biological functions and cell penetration.
• Understanding cyclotide-membrane interactions can guide the development of novel peptide-based therapeutics.
• Distinct cyclotide subfamilies exhibit varied membrane interaction profiles, impacting their potential applications.