title: Identification of a novel four-domain member of the proteinase inhibitor II family from the stigmas of Nicotiana alata.
abstract: Proteinase inhibitors (PIs) of the potato type II family have been identified in a number of solanaceous species. Most family members have two PI domains which are specific for either chymotrypsin or trypsin. More recently family members have been described with three or six repeated PI domains. Here we describe a novel four-domain family member produced in the stigmas and leaves of the ornamental tobacco, Nicotiana alata, which has high sequence identity with a six-domain member from the same species. Both proteins are produced as precursors that enter the secretory pathway and are subsequently processed into a series of 6 kDa Pis. The four- and six-domain precursor proteins were isolated from immature stigmas and characterised by mass spectrometry which revealed that both proteins had been trimmed at the N-terminus, at a position corresponding to the predicted signal peptide cleavage site. Furthermore, no post-translational modifications were apparent.
authors.affiliation: Department of Biochemistry and Genetics, LaTrobe University, Bundoora, Australia.
authors.forename: E A
authors.initials: EA
authors.lastname: Miller
authors.forename: M C
authors.initials: MC
authors.lastname: Lee
authors.forename: A H
authors.initials: AH
authors.lastname: Atkinson
authors.forename: M A
authors.initials: MA
authors.lastname: Anderson
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D010450:Endopeptidases / Q000378:metabolism; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018514:Plant Structures / Q000235:genetics / Q000378:metabolism; D010947:Plants, Toxic; D011480:Protease Inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D011498:Protein Precursors / Q000302:isolation & purification; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000235:genetics* / Q000254:growth & development
chemical_list: D018076:DNA, Complementary; D010940:Plant Proteins; D011480:Protease Inhibitors; D011498:Protein Precursors; D010450:Endopeptidases