Chemical Synthesis and Functional Analysis of VarvA Cyclotide.

Claudio Álvarez,María Romero,Fernando Albericio,Fanny Guzmán,Paula Santana,Omar Luna,Constanza Cárdenas

doi:10.3390/molecules23040952

Abstract

Cyclotides are circular peptides found in various plant families. A cyclized backbone, together with multiple disulfide bonds, confers the peptides’ exceptional stability against protease digestion and thermal denaturation. In addition, the features of these antimicrobial molecules make them suitable for use in animal farming, such as aquaculture. Fmoc solid phase peptide synthesis on 2-chlorotrityl chlorine (CTC) resin using the “tea-bag” approach was conducted to generate the VarvA cyclotide identified previously from Viola arvensis. MALDI-TOF mass spectrometry determined the correct peptide amino acid sequence and the cyclization sites-critical in this multicyclic compound. The cyclotide showed antimicrobial activity against various Gram-negative bacteria, including recurrent pathogens present in Chilean aquaculture. The highest antimicrobial activity was found to be against Flavobacterium psychrophilum. In addition, membrane blebbing on the bacterial surface after exposure to the cyclotide was visualized by SEM microscopy and the Sytox Green permeabilization assay showed the ability to disrupt the bacterial membrane. We postulate that this compound can be proposed for the control of fish farming infections.

Highlights

Cyclic peptides have attracted great interest in recent years due to their increased stability over linear peptides and wide range of bioactivities [1].Most peptides show a linear structure with open ends, which makes them targets for proteolytic enzymes, decreasing their bioavailability [2,3]
The Fmoc-solid-phase peptide synthesis (SPPS) chemical synthesis approach on 2-chlorotrityl chlorine (CTC) resin was used for the VarvA cyclotide synthesis
[40,41].,the theability abilitytotochemically chemically synthesize synthesizecyclotides cyclotidesisisan animportant importantgoal, goal,both bothfor forthe thepractical practicalpurpose purposeof ofmutagenesis mutagenesisstudies studiesto to understand their mechanism of action, as well as studies of new pharmaceutical applications

Summary

Introduction

Cyclic peptides have attracted great interest in recent years due to their increased stability over linear peptides and wide range of bioactivities [1].Most peptides show a linear structure with open ends, which makes them targets for proteolytic enzymes, decreasing their bioavailability [2,3]. Cyclic peptides have attracted great interest in recent years due to their increased stability over linear peptides and wide range of bioactivities [1]. Cyclic peptides have the unique feature that their N and C termini are joined in an amide bond to form a cyclic backbone, and they show greater stability than their linear counterparts [4,5,6,7,8]. Measuring 28–37 amino acid residues in length, cyclotides are the largest known family of cyclic peptides [9]. The six highly conserved cysteine residues of cyclotides lead to a knotted arrangement of three disulfide bonds. An embedded ring is formed by two disulfide bonds and their connecting backbone segments, and the third disulfide bond

Methods

Results

Discussion

Conclusion