title: Activity of the C-terminal-dependent vacuolar sorting signal of horseradish peroxidase C1a is enhanced by its secondary structure.
abstract: Plant class III peroxidase (PRX) catalyzes the oxidation and oxidative polymerization of a variety of phenolic compounds while reducing hydrogen peroxide. PRX proteins are classified into apoplast type and vacuole type based on the absence or the presence of C-terminal propeptides, which probably function as vacuolar sorting signals (VSSs). In this study, in order to improve our understanding of vacuole-type PRX, we analyzed regulatory mechanisms of vacuolar sorting of a model vacuole-type PRX, the C1a isozyme of horseradish (Armoracia rusticana) (HRP C1a). Using cultured transgenic tobacco cells and protoplasts derived from horseradish leaves, we characterized HRP C1a's VSS, which is a 15 amino acid C-terminal propeptide (C15). We found that the C-terminal hexapeptide of C15 (C6), which is well conserved among vacuole-type PRX proteins, forms the core of the C-terminal-dependent VSS. We also found that the function of C6 is enhanced by the remaining N-terminal part of C15 which probably folds into an amphiphilic α-helix.
authors.affiliation: Graduate School of Biological Sciences, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama-cho, Ikoma, Nara, 630-0101 Japan. t-matsui@bs.naist.jp
authors.forename: Takeshi
authors.initials: T
authors.lastname: Matsui
authors.forename: Ayako
authors.initials: A
authors.lastname: Tabayashi
authors.forename: Megumi
authors.initials: M
authors.lastname: Iwano
authors.forename: Atsuhiko
authors.initials: A
authors.lastname: Shinmyo
authors.forename: Ko
authors.initials: K
authors.lastname: Kato
authors.forename: Hideki
authors.initials: H
authors.lastname: Nakayama
mesh_terms: D000595:Amino Acid Sequence; D031215:Armoracia / Q000201:enzymology*; D002478:Cells, Cultured; D006735:Horseradish Peroxidase / Q000737:chemistry*; D007527:Isoenzymes / Q000378:metabolism; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified / Q000378:metabolism; D010957:Plasmids; D021382:Protein Sorting Signals; D017433:Protein Structure, Secondary; D011523:Protoplasts / Q000378:metabolism; D014026:Nicotiana / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism*
chemical_list: D007527:Isoenzymes; D021382:Protein Sorting Signals; D006735:Horseradish Peroxidase