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.
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.
Ohtsubo
Sadami
S
Food Research Center, Niigata Agricultural Research Institute, Kamo, Niigata 959-1381, Japan. ootsubo@ari.pref.niigata.jp
Taiyoji
Mayumi
M
Kawase
Tomokazu
T
Taniguchi
Masayuki
M
Saitoh
Eiichi
E
D002850:Chromatography, Gel; D015891:Cystatins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019281:Dimerization; D006358:Hot Temperature; D012275:Oryza / Q000201:enzymology*; D011994:Recombinant Proteins
D015891:Cystatins; D011994:Recombinant Proteins