Nagata K, Kudo N, Abe K, Arai S, Tanokura M
Biotechnology Research Center and Department of Applied Biological Chemistry, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
Biochemistry. 2000 Dec 5;39(48):14753-60. doi: 10.1021/bi0006971.
The three-dimensional structure of oryzacystatin-I, a cysteine proteinase inhibitor of the rice, Oryza sativa L. japonica, has been determined in solution at pH 6.8 and 25 degrees C by (1)H and (15)N NMR spectroscopy. The main body (Glu13-Asp97) of oryzacystatin-I is well-defined and consists of an alpha-helix and a five-stranded antiparallel beta-sheet, while the N- and C-terminal regions (Ser2-Val12 and Ala98-Ala102) are less defined. The helix-sheet architechture of oryzacystatin-I is stabilized by a hydrophobic cluster formed between the alpha-helix and the beta-sheet and is considerably similar to that of monellin, a sweet-tasting protein from an African berry, as well as those of the animal cystatins studied, e.g., chicken egg white cystatin and human stefins A and B (also referred to as human cystatins A and B). Detailed structural comparison indicates that oryzacystatin-I is more similar to chicken cystatin, which belongs to the type-2 animal cystatins, than to human stefins A and B, which belong to the type-1 animal cystatins, despite different loop length.
利用氢核磁共振（¹H NMR）和氮-15核磁共振（¹⁵N NMR）光谱技术，在pH值为6.8、温度为25℃的溶液中测定了粳稻（Oryza sativa L. japonica）半胱氨酸蛋白酶抑制剂水稻半胱氨酸蛋白酶抑制剂-I（oryzacystatin-I）的三维结构。水稻半胱氨酸蛋白酶抑制剂-I的主体结构（Glu13-Asp97）清晰可辨，由一个α螺旋和一个五股反平行β折叠组成，而N端和C端区域（Ser2-Val12和Ala98-Ala102）则不太明确。水稻半胱氨酸蛋白酶抑制剂-I的螺旋-折叠结构通过α螺旋和β折叠之间形成的疏水簇得以稳定，这与来自非洲浆果的甜味蛋白莫内林以及所研究的动物半胱氨酸蛋白酶抑制剂（如鸡蛋白半胱氨酸蛋白酶抑制剂和人类激肽释放酶抑制蛋白A和B，也称为人类半胱氨酸蛋白酶抑制剂A和B）的结构相当相似。详细的结构比较表明，尽管环长度不同，但水稻半胱氨酸蛋白酶抑制剂-I与属于2型动物半胱氨酸蛋白酶抑制剂的鸡半胱氨酸蛋白酶抑制剂的相似性高于与属于1型动物半胱氨酸蛋白酶抑制剂的人类激肽释放酶抑制蛋白A和B的相似性。
