title: Solution structure of bromelain inhibitor IV from pineapple stem: structural similarity with Bowman-Birk trypsin/chymotrypsin inhibitor from soybean.
abstract: Bromelain inhibitor VI from pineapple stem (BI-VI) is a unique double-chain inhibitor with an 11-residue light chain and a 41-residue heavy chain by disulfide bonds and inhibits the cysteine proteinase bromelain competitively. The structure of BI-VI in aqueous solution was determined using nuclear magnetic resonance spectroscopy and simulated annealing-based calculations. Its three-dimensional structure was shown to be composed of two distinct domains, each of which is formed by a three-stranded antiparallel beta-sheet. Unexpectedly, BI-VI was found to share a similar folding and disulfide bond connectivities not with cystatin superfamily inhibitors which inhibit the same cysteine proteinases but with the Bowman-Birk trypsin/chymotrypsin inhibitor from soybean (BBI-I). BBI-I is a 71-residue inhibitor which has two independent inhibitory sites toward the serine proteinases trypsin and chymotrypsin. These structural similarities with BBI-I suggest that they have evolved from a common ancestor and differentiated in function during a course of molecular evolution.
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; D015853:Cysteine Proteinase Inhibitors / Q000737:chemistry*; D005638:Fruit; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000648:ultrastructure*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012996:Solutions; D013329:Structure-Activity Relationship; D014358:Trypsin Inhibitor, Bowman-Birk Soybean / Q000648:ultrastructure*
chemical_list: C095959:BI-VI protein, Ananas comosus; D015853:Cysteine Proteinase Inhibitors; D010940:Plant Proteins; D012996:Solutions; D014358:Trypsin Inhibitor, Bowman-Birk Soybean