An Orbitide from Ratibida columnifera Seed Containing 16 Amino Acid Residues

J Nat Prod. 2019 Aug 23;82(8):2152-2158. doi: 10.1021/acs.jnatprod.9b00111. Epub 2019 Aug 8.


Cyclic peptides are abundant in plants and have attracted interest due to their bioactivity and potential as drug scaffolds. Orbitides are head-to-tail cyclic peptides that are ribosomally synthesized, post-translationally modified, and lack disulfide bonds. All known orbitides contain 5-12 amino acid residues. Here we describe PLP-53, a novel orbitide from the seed of Ratibida columnifera. PLP-53 consists of 16 amino acids, four residues larger than any known orbitide. NMR structural studies showed that, compared to previously characterized orbitides, PLP-53 is more flexible and, under the studied conditions, did not adopt a single ordered conformation based on analysis of NOEs and chemical shifts.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Amino Acids / analysis*
  • Mass Spectrometry
  • Nuclear Magnetic Resonance, Biomolecular
  • Peptides, Cyclic / chemistry
  • Peptides, Cyclic / isolation & purification*
  • Protein Conformation
  • Ratibida / embryology*
  • Seeds / chemistry*


  • Amino Acids
  • Peptides, Cyclic