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Plant Direct. 2018 Feb;2(2). pii: e00042. doi: 10.1002/pld3.42. Epub 2018 Feb 28.

A family of small, cyclic peptides buried in preproalbumin since the Eocene epoch.

Author information

1
The University of Western Australia, School of Molecular Sciences, 35 Stirling Highway, Crawley, Perth 6009, Australia.
2
ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia, 35 Stirling Highway, Crawley, Perth 6009, Australia.
3
Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, 35 Stirling Highway, Crawley, Perth 6009, Australia.
4
Department of Animal, Plant and Soil Sciences, School of Life Sciences & ARC Centre of Excellence in Plant Energy Biology, AgriBio, The Centre for AgriBioscience, La Trobe University, Bundoora 3086, VIC, Australia.
5
Marshall Centre for Infectious Disease Research and Training, School of Biomedical Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, Perth 6009, Australia.
6
Department of Computer Science & Engineering, University of California, 9500 Gilman Drive, La Jolla, San Diego, CA 92093-0404, USA.

Abstract

Orbitides are cyclic ribosomally-synthesized and post-translationally modified peptides (RiPPs) from plants; they consist of standard amino acids arranged in an unbroken chain of peptide bonds. These cyclic peptides are stable and range in size and topologies making them potential scaffolds for peptide drugs; some display valuable biological activities. Recently two orbitides whose sequences were buried in those of seed storage albumin precursors were said to represent the first observable step in the evolution of larger and hydrophilic bicyclic peptides. Here, guided by transcriptome data, we investigated peptide extracts of 40 species specifically for the more hydrophobic orbitides and confirmed 44 peptides by tandem mass spectrometry, as well as obtaining solution structures for four of them by NMR. Acquiring transcriptomes from the phylogenetically important Corymboideae family confirmed the precursor genes for the peptides (called PawS1-Like or PawL1) are confined to the Asteroideae, a subfamily of the huge plant family Asteraceae. To be confined to the Asteroideae indicates these peptides arose during the Eocene epoch around 45 Mya. Unlike other orbitides, all PawL-derived Peptides contain an Asp residue, needed for processing by asparaginyl endopeptidase. This study has revealed what is likely to be a very large new family of orbitides, uniquely buried alongside albumin and processed by asparaginyl endopeptidase.

KEYWORDS:

Asteraceae; asparaginyl endopeptidase; cyclic peptide; orbitide; seed storage albumin

PMID:
30417166
PMCID:
PMC6223261
[Available on 2019-02-01]
DOI:
10.1002/pld3.42

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