title: Albumins and their processing machinery are hijacked for cyclic peptides in sunflower.
abstract: The cyclic peptide sunflower trypsin inhibitor 1 (SFTI-1) blocks trypsin and is a promising drug lead and protein engineering scaffold. We show that SFTI-1 and the newfound SFT-L1 are buried within PawS1 and PawS2, precursors for seed storage protein albumins. Proalbumins are matured by asparaginyl endopeptidase, which we show is required to liberate both ends of SFTI-1 as well as to mature PawS1 albumin. Thus, these peptides emerge from within an albumin precursor by the action of albumin's own processing enzyme.
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia. j.mylne@imb.uq.edu.au
authors.forename: Joshua S
authors.initials: JS
authors.lastname: Mylne
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Colgrave
authors.forename: Norelle L
authors.initials: NL
authors.lastname: Daly
authors.forename: Aurelie H
authors.initials: AH
authors.lastname: Chanson
authors.forename: Alysha G
authors.initials: AG
authors.lastname: Elliott
authors.forename: Emily J
authors.initials: EJ
authors.lastname: McCallum
authors.forename: Alun
authors.initials: A
authors.lastname: Jones
authors.forename: David J
authors.initials: DJ
authors.lastname: Craik
mesh_terms: D000418:Albumins / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D003546:Cysteine Endopeptidases / Q000378:metabolism; D006368:Helianthus / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D010456:Peptides, Cyclic / Q000737:chemistry / Q000378:metabolism*; D011228:Prealbumin / Q000378:metabolism; D055314:Seed Storage Proteins / Q000737:chemistry / Q000378:metabolism; D014361:Trypsin Inhibitors / Q000737:chemistry / Q000494:pharmacology; D000099240:Asparaginyl Endopeptidase
chemical_list: D000418:Albumins; D003546:Cysteine Endopeptidases; D010456:Peptides, Cyclic; D011228:Prealbumin; D055314:Seed Storage Proteins; D014361:Trypsin Inhibitors; D000099240:Asparaginyl Endopeptidase; C448501:SFTI-1 peptide, sunflower