title: Oryzacystatin-II, a cystatin from rice (Oryza sativa L. japonica), is a dimeric protein: possible involvement of the interconversion between dimer and monomer in the regulation of the reactivity of oryzacystatin-II.
abstract: We examined the biochemical and structural properties of oryzacystatin-II, a phytocystatin in rice (Oryza sativa L. japonica), under heat-stress conditions. The enzyme inhibitory reactivity of oryzacystatin-II was enhanced by heating in a temperature-dependent manner and reached a maximum level by heating at 65 degrees C for 10 min. Size-exclusion chromatography showed that oryzacystatin-II forms a homodimer at ambient temperature and that the enhancement of inhibitory reactivity is due to the conversion of the dimeric to a monomeric form. The monomeric form of oryzacystatin-II reverted to the dimer during storage at 4 degrees C, suggesting that dimerization is an intrinsic property of oryzacystatin-II. The affinity of the monomer for cysteine proteinases was significantly higher than that of the dimer. This is the first paper to describe the noncovalent dimerization for a cystatin under nonstress conditions.
authors.affiliation: Food Research Center, Niigata Agricultural Research Institute, Kamo, Niigata 959-1381, Japan. ootsubo@ari.pref.niigata.jp
authors.forename: Sadami
authors.initials: S
authors.lastname: Ohtsubo
authors.forename: Mayumi
authors.initials: M
authors.lastname: Taiyoji
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Kawase
authors.forename: Masayuki
authors.initials: M
authors.lastname: Taniguchi
authors.forename: Eiichi
authors.initials: E
authors.lastname: Saitoh
mesh_terms: D002850:Chromatography, Gel; D015891:Cystatins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019281:Dimerization; D006358:Hot Temperature; D012275:Oryza / Q000201:enzymology*; D011994:Recombinant Proteins
chemical_list: D015891:Cystatins; D011994:Recombinant Proteins