Molecular cloning and characterization of oryzacystatin-III, a novel member of phytocystatin in rice (Oryza sativa L. japonica) |
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Authors: | Ohtsubo Sadami Kobayashi Hitoshi Noro Wataru Taniguchi Masayuki Saitoh Eiichi |
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Institution: | Food Research Center, Niigata Agricultural Research Institute, Kamo, Japan. ootsubo@ari.pref.niigata.jp |
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Abstract: | On the basis of cDNA sequences, we found that the calli of rice encodes an amino acid sequence that shares 56% and 89% identity, respectively, with oryzacystatin-I and oryzacystatin-II. This sequence differs from that of oryzacystatin-II in the N-terminal region (Gln(7)-Ala(19) in the oryzacystatin-III numbering), and this region contained a glycine residue (Gly(14)), which is evolutionarily conserved in the cystatin superfamily. We named this novel protein oryzacystatin-III. Nucleotide sequencing of the 5'-flanking region of the oryzacystatin-III gene showed that it is highly homologous to the oryzacystatin-II gene but distinct from the oryzacystatin-II locus. Oryzacystatin-III inhibited papain, ficin, and human cathepsin B. The inhibition constants for papain and ficin differ from those of oryzacystatin-I and -II, and cathepsin B activity is affected only by oryzacystatin-III, showing differences in the interaction of these inhibitors with enzymes. These data suggest that the above three inhibitors may play unique physiological roles in the regulations of rice cysteine proteinases. |
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