title: Different disulfide bridge connectivity drives alternative folds in highly homologous Brassicaceae trypsin inhibitors.
abstract: Low-molecular-mass trypsin inhibitors from Arabidopsis thaliana, Brassica napus var. oleifera, and Sinapis alba L. (ATTI, RTI, and MTI, respectively) display more than 69% amino acid sequence identity. Among others, the amino acid sequence Cys-Ala-Pro-Arg-Ile building up the inhibitor reactive site, and the eight Cys residues forming four disulfide bridges are conserved. However, the disulfide bridge connectivity of RTI and MTI (C1-C3, C2-C4, C5-C6, and C7-C8) is different from that of ATTI Cys (C1-C8, C2-C5, C3-C6, and C4-C7). Despite the different disulfide bridge connectivity, the reactive site loop of ATTI, RTI, and MTI is solvent exposed permitting trypsin recognition. Structural considerations here reported suggest that proteins showing high amino acid sequence identity and common functional properties could display different three-dimensional structures. This may reflect high inhibitor plasticity in relation to plant-pathogen interactions, plant tissue development as well as the different redox potential of cell compartments.
authors.affiliation: Laboratorio Interdipartimentale di Microscopia Elettronica, Università Roma Tre, Roma, Italy.
authors.forename: Loris
authors.initials: L
authors.lastname: Leboffe
authors.affiliation: Dipartimento di Scienze, Università Roma Tre, Roma, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Angelini
authors.affiliation: Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Ferrara, Ferrara, Italy.
authors.forename: Enea
authors.initials: E
authors.lastname: Menegatti
authors.affiliation: Dipartimento di Scienze, Università Roma Tre, Roma, Italy.|Istituto Nazionale di Fisica Nucleare, Sezione Università Roma Tre, Roma, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Polticelli
authors.affiliation: Laboratorio Interdipartimentale di Microscopia Elettronica, Università Roma Tre, Roma, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Ascenzi
mesh_terms: D000595:Amino Acid Sequence; D019607:Brassicaceae / Q000737:chemistry*; D004220:Disulfides / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry; D017510:Protein Folding; D040681:Structural Homology, Protein; D014361:Trypsin Inhibitors / Q000737:chemistry* / Q000378:metabolism; D014362:Trypsinogen / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D004220:Disulfides; D010940:Plant Proteins; D014361:Trypsin Inhibitors; D014362:Trypsinogen
keywords: Arabidopsis thaliana; Brassica napus var. oleifera; Sinapis alba L; disulfide bridge connectivity; plant trypsin inhibitors; primary structure; three-dimensional structure