The genetic origin of evolidine, the first cyclopeptide discovered in plants, and related orbitides

Abstract

Cyclic peptides are reported to have antibacterial, antifungal and other bioactivities. Several genera of the Rutaceae family are known to produce orbitides, which are small head-to-tail cyclic peptides composed of proteinogenic amino acids and lacking disulfide bonds. Melicope xanthoxyloides is an 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, but here we use tandem mass spectrometry to rediscover evolidine and using de novo transcriptomics we show its biosynthetic origin to be from a short precursor just 48 residues in length. In all, seven M. xanthoxyloides orbitides were found and they had atypically diverse C-termini consisting of residues not recognized by either of the known proteases plants use to macrocyclize peptides. Two of the novel orbitides were studied by nuclear magnetic resonance spectroscopy and although one had definable structure, the other did not. By mining RNA-seq and whole genome sequencing data from other species, it was apparent that a large and diverse family of peptides is encoded by sequences like these across the Rutaceae.

Structural Characterization of the PawL-Derived Peptide Family, an Ancient Subfamily of Orbitides

“…The copyright holder for this preprint (which this version posted July 19, 2021. ; https://doi.org/10.1101/2021.07.18.452857 doi: bioRxiv preprint -10, 14 -12 14 and -53 29 and orbitides jatrophidin, 23 pohlianin C, 23 ribifolin 23 and xanthoxycyclin D 30 ). Negatively charged residues (Asp and Glu) and positively charged residues (Arg, His and Lys) are highlighted in red and blue respectively.…”

“…Peptides were purified to >95 % by RP-HPLC and their identity confirmed by ESI-MS. -10, 14 -12 14 and -53 29 and orbitides jatrophidin, 23 pohlianin C, 23 ribifolin 23 and xanthoxycyclin D 30 ). Negatively charged residues (Asp and Glu) and positively charged residues (Arg, His and Lys) are highlighted in red and blue respectively.…”

“…Peptides were purified to >95 % purity by RP-HPLC and their identity confirmed by ESI-MS (Figure 1 in Supplementary Information). and -46) aligned with sequences for which structures have previously been solved (PLPs -2, 14 -4, 14 -10, 14 -12 14 and -53 29 and the non-PLP orbitides jatrophidin, 23 pohlianin C, 23 ribifolin 23 and xanthoxycyclin D 31 ). Negatively charged residues (Asp and Glu) and positively charged residues (Arg, His and Lys) are highlighted in red and blue respectively.…”