title: Primary structure, sequence-specific 1H-NMR assignments and secondary structure in solution of bromelain inhibitor VI from pineapple stem.
abstract: One of the bromelain inhibitors, isoinhibitor VI (BI-VI), was purified from pineapple stem powder and its complete amino acid sequence was determined by conventional protein sequencing. These results revealed that the protein consists of an 11-residue light chain and a 41-residue heavy chain, cross-linked to each other by disulfide bonds to form the native inhibitor of 52 residues (M(r) = 5888). The secondary structure of BI-VI was analyzed based on the sequence-specific 1H resonance assignment of its two-dimensional NMR spectra. BI-VI was shown to be composed of two domains (A and B) which are formed by antiparallel beta-sheets, but has no alpha-helix. These results were consistent with the CD spectra of BI-VI. Residues Lys27-Ile29 (heavy chain) form a triple-stranded antiparallel beta-sheet with residues Asp9-Tyr11 and Lys22-Glu24 (heavy chain) in the A domain and residues Cys5-Cys7 (heavy chain) form another triple-stranded beta-sheet with residues Cys6-Cys8 (light chain) and Asp32-Ile34 (heavy chain) in the B domain. The secondary structure as well as the primary structure of BI-VI was distinctly different from that of the other cysteine protease inhibitor, cystatin, and from that of basic pancreatic trypsin inhibitor.
authors.affiliation: Department of Biophysics and Biochemistry, Faculty of Science, University of Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Hatano
authors.forename: M
authors.initials: M
authors.lastname: Kojima
authors.forename: M
authors.initials: M
authors.lastname: Tanokura
authors.forename: K
authors.initials: K
authors.lastname: Takahashi
mesh_terms: D000595:Amino Acid Sequence; D001963:Bromelains / Q000037:antagonists & inhibitors*; D002942:Circular Dichroism; D015853:Cysteine Proteinase Inhibitors / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology; D011392:Proline / Q000737:chemistry; D017433:Protein Structure, Secondary
chemical_list: C095959:BI-VI protein, Ananas comosus; D015853:Cysteine Proteinase Inhibitors; D010940:Plant Proteins; D001963:Bromelains; D011392:Proline; C091760:stem bromelain