Project description:<p>Cyclic peptides are reported to have antibacterial, antifungal and other bioactivities. Orbitides are a class of cyclic peptide that are small, head-to-tail cyclized, composed of proteinogenic amino acids, and lack disulfide bonds; they are also known in several genera of the plant family Rutaceae. Melicope xanthoxyloides is the Australian rain forest tree of the Rutaceae family in which evolidine - the first plant cyclic peptide - was discovered. Evolidine (cyclo-SFLPVNL) has subsequently been all but forgotten in the academic literature, so to redress this we used tandem mass spectrometry and de novo transcriptomics to rediscover evolidine and decipher its biosynthetic origin from a short precursor just 48 residues in length. We also identify another six M. xanthoxyloides orbitides using the same techniques. These peptides have atypically diverse C-termini consisting of residues not recognized by either of the known proteases plants use to macrocyclize peptides, suggesting new cyclizing enzymes a wait discovery. We examined the structure of two of the novel orbitides by NMR, finding one had a definable structure, whereas the other did not. Mining RNA-seq and whole genome sequencingdata from other species of the Rutaceae familyrevealed a large and diverse family of peptides is encoded by similar sequences across the family and demonstrates how powerful de novo transcriptomics can be at accelerating the discovery of new peptide families.</p>
2020-10-14 | MTBLS1963 | MetaboLights
Project description:Biosynthesis of cyclic peptides in Oldenlandia
Project description:We report a new platform for the rapid phenotypic selection of protein aggregation inhibitors from genetically encoded cyclic peptide libraries in E. coli based on phage-assisted continuous evolution (PACE). Here, we developed a new PACE-compatible selection for protein aggregation inhibition and employed it to identify cyclic peptides that suppress amyloid-β42 (Aβ42) and human islet amyloid polypeptide (hIAPP) aggregation. Additionally, we integrated a negative selection that removes false positives and off-target hits, significantly improving cyclic peptide selectivity. We show that selected inhibitors are active when chemically re-synthesized in in vitro assays. Our platform provides a powerful new approach for the rapid discovery of cyclic peptide inhibitors of protein aggregation and may serve as the basis for the future evolution of cyclic peptides with a broad spectrum of inhibitory activities. Data deposited here are HTS data critical to the conclusions of this study.