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

• Published in: Plant physiology (Bethesda) 1994-10, Vol.106 (2), p.771-777
• Main Authors: McManus, M.T. (AgReseach, Palmerston North, New Zealand), Laing, W.A, Christeller, J.T, White, D.W.R
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino acids; Antibodies; ANTIMETABOLITE; ANTIMETABOLITOS; Chromatography; Chymotrypsin - antagonists & inhibitors; CHYMOTRYPSINE; COMPOSICION QUIMICA; COMPOSITION CHIMIQUE; EXPRESION GENICA; EXPRESSION DES GENES; GENETICA; GENETIQUE; INHIBIDORES DE ENZIMAS; INHIBITEUR D'ENZYME; Leaves; Molecular Biology and Gene Regulation; Molecular Sequence Data; Multigene Family; Nicotiana; NICOTIANA TABACUM; Peptide Fragments - chemistry; Peptide Fragments - isolation & purification; Plant Proteins - biosynthesis; Plant Proteins - chemistry; Plant Proteins - metabolism; PLANTAS TRANSGENICAS; PLANTE TRANSGENIQUE; Plants, Genetically Modified; Plants, Toxic; PROTEASAS; PROTEASE; Protease inhibitors; Protease Inhibitors - chemistry; Protein Processing, Post-Translational; PROTEINAS; PROTEINE; Proteins; PURIFICACION; PURIFICATION; QUIMOTRIPSINA; Regional identity; Sequence Homology, Amino Acid; Sequencing; SINTESIS DE PROTEINAS; SOLANUM TUBEROSUM; Solanum tuberosum - genetics; Solanum tuberosum - metabolism; SYNTHESE PROTEIQUE; TRANSFERENCIA DE GENES; TRANSFERT DE GENE; Transgenic plants; Tubers
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.106.2.771

A member of the potato proteinase inhibitor II (PPI-II) gene family under the control of the cauliflower mosaic virus 35S promoter has been introduced into tobacco (Nicotiana tabacum). Purification of the PPI-II protein that accumulates in transgenic tobacco has confirmed that the N-terminal signal sequence is removed and that the inhibitor accumulates as a protein of the expected size (21 kD). However a smaller peptide of approximately 5.4 kD has also been identified as a foreign gene product in transgenic tobacco plants. This peptide is recognized by an antiPPI-II antibody inhibits the serine proteinase chymotrypsin and is not observed in nontransgenic tobacco. Furthermore amino acid sequencing demonstrates that the peptide is identical to a lower molecular weight chymotrypsin inhibitor found in potato tubers and designated as potato chymotrypsin inhibitor I (PCI-I). Together, these data confirm that as postulated to occur in potato PCI-I does arise from the full-length PPI-II protein by posttranslational processing. The use of transgenic tobacco represents an ideal system with which to determine the precise mechanism by which this protein modification occurs