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Nat Struct Biol. 1999 Jun;6(6):526-30.

A novel two-chain proteinase inhibitor generated by circularization of a multidomain precursor protein.

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School of Biochemistry, La Trobe University, Bundoora, Victoria, Australia.


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.

[Indexed for MEDLINE]

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