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.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Binding Sites
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Chymotrypsin / antagonists & inhibitors
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Crystallization
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Disulfides / chemistry
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Disulfides / metabolism
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Evolution, Molecular
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Gene Duplication
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Molecular Sequence Data
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Molecular Weight
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Nicotiana / chemistry
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Nuclear Magnetic Resonance, Biomolecular
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Peptide Fragments / chemistry*
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Peptide Fragments / metabolism
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Plant Proteins / chemistry*
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Plant Proteins / isolation & purification
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Plant Proteins / metabolism
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Plant Structures / chemistry
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Plants, Toxic
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Protease Inhibitors*
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Protein Conformation
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Protein Folding
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Protein Precursors / chemistry
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Protein Precursors / metabolism*
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Protein Structure, Secondary
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Repetitive Sequences, Amino Acid
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Serine Proteinase Inhibitors / chemistry*
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Serine Proteinase Inhibitors / isolation & purification
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Serine Proteinase Inhibitors / metabolism
Substances
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Disulfides
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Peptide Fragments
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Plant Proteins
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Protease Inhibitors
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Protein Precursors
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Serine Proteinase Inhibitors
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proteinase inhibitor II protein, plant
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proteinase inhibitor I (plants)
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Chymotrypsin