A novel two-chain proteinase inhibitor generated by circularization of a multidomain precursor protein. |
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Authors: | M C Lee M J Scanlon D J Craik M A Anderson |
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Institution: | School of Biochemistry, La Trobe University, Bundoora, Victoria, Australia. |
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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. |
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