title: A novel two-chain proteinase inhibitor generated by circularization of a multidomain precursor protein.
abstract: Female reproductive tissues of the ornamental tobacco amass high levels of serine proteinase inhibitors (PIs) for protection against pests and pathogens. These PIs are produced from a precursor protein composed of six repeats each with a protease reactive site. Here we show that proteolytic processing of the precursor generates five single-chain PIs and a remarkable two-chain inhibitor formed by disulfide-bond linkage of N- and C-terminal peptide fragments. Surprisingly, PI precursors adopt this circular structure regardless of the number of inhibitor domains, suggesting this bracelet-like conformation is characteristic of the widespread potato inhibitor II (Pot II) protein family.
authors.affiliation: School of Biochemistry, La Trobe University, Bundoora, Victoria, Australia.
authors.forename: M C
authors.initials: MC
authors.lastname: Lee
authors.forename: M J
authors.initials: MJ
authors.lastname: Scanlon
authors.forename: D J
authors.initials: DJ
authors.lastname: Craik
authors.forename: M A
authors.initials: MA
authors.lastname: Anderson
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002918:Chymotrypsin / Q000037:antagonists & inhibitors; D003460:Crystallization; D004220:Disulfides / Q000737:chemistry / Q000378:metabolism; D019143:Evolution, Molecular; D020440:Gene Duplication; D008969:Molecular Sequence Data; D008970:Molecular Weight; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D018514:Plant Structures / Q000737:chemistry; D010947:Plants, Toxic; D011480:Protease Inhibitors; D011487:Protein Conformation; D017510:Protein Folding; D011498:Protein Precursors / Q000737:chemistry / Q000378:metabolism*; D017433:Protein Structure, Secondary; D020449:Repetitive Sequences, Amino Acid; D015842:Serine Proteinase Inhibitors / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D014026:Nicotiana / Q000737:chemistry
chemical_list: D004220:Disulfides; D010446:Peptide Fragments; D010940:Plant Proteins; D011480:Protease Inhibitors; D011498:Protein Precursors; D015842:Serine Proteinase Inhibitors; C034104:proteinase inhibitor II protein, plant; C023578:proteinase inhibitor I (plants); D002918:Chymotrypsin