Proteinase inhibitors in Nicotiana alata stigmas are derived from a precursor protein which is processed into five homologous inhibitors.

Posttranslational Modification of an Isoinhibitor from the Potato Proteinase Inhibitor II Gene Family in Transgenic Tobacco Yields a Peptide with Homology to Potato Chymotrypsin Inhibitor I

“…The processing of a precursor 42-kD PPI-11-related polypeptide to give a series of smaller isoinhibitors has been observed in stigmas from Nicotiana alata flowers (Atkinson et al, 1993). A series of six small isoinhibitors has been identified in wounded leaves of N. tabacum (Pearce et al, 1903;McManus et al, 1994), although a larger precursor protein has not yet been identified.…”

Identification and Characterization of a Prevacuolar Compartment in Stigmas of Nicotiana alata

“…Buffer-soluble proteins were isolated from immature (preanthesis) and mature (postanthesis) stigmas, as described by Atkinson et al (1993). Proteins were subjected to SDS-PAGE, and immunoblotting experiments were conducted (described below) using antibodies raised against purified 6-kD PIs (anti-PI; 1:1000 dilution of purified IgG, 1 mg/mL; Atkinson et al, 1993) and antibodies raised to the CTPP helical domain (anti-CTPP; 1:1000 dilution of crude serum). The specificity of the anti-CTPP antibodies was demonstrated by preincubating a 1:200 dilution of crude serum with a 20-fold molar excess of free synthetic peptide for 1 hr at room temperature.…”

“…In addition to these vacuolar proteins, they also secrete copious amounts of extracellular mucilage that is rich in lipid and protein. Na-PI is a 40-kD multidomain precursor protein that consists of six repeated domains, each with an inhibitory site for either chymotrypsin or trypsin (Atkinson et al, 1993). In addition to the six repeated inhibitor domains, Na-PI also has an ER signal peptide and a C-terminal domain of 25 amino acids that is rich in acidic and hydrophobic residues.…”

“…Stigmas are an ideal system in which to study the secretory pathway because they accumulate large amounts of a series of proteinase inhibitors (PIs) in the central vacuole (Atkinson et al, 1993;E.A. Miller, I. Bönig, and M.A.…”

Reply: The Role of BP-80 in Sorting to the Vacuole in Stigmas

“…Jiang and Rogers raise some important issues regarding the complexity of protein traffic to the vacuole in plant cells, a topic that we have studied by examining vacuolar transport of a multidomain precursor protein (Na-PI) that is very highly expressed in stigmas of Nicotiana alata (Atkinson et al, 1993). Using this system, we identified a prevacuolar compartment that appeared to be involved in transport of Na-PI to the vacuole.…”