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水稻Bowman-Birk蛋白酶抑制剂(RBBI)在体外是胰蛋白酶抑制剂,有的有1个同源结构域(8kD),有的有2个同源结构域(16kD).本研究发现,在水稻体内存在带有3个同源结构域的RBBI(25kD),而且RBBI受发育和伤害调控.体外实验发现,3:13二硫键(而不是4:5二硫键)可抑制胰蛋白酶的活性;而RBBI3-1的D3结构域对胰蛋白酶、胰凝乳蛋白酶、木瓜蛋白酶和枯草芽孢杆菌素没有抑制活性.突变实验表明,改变D1结构域N端的P1位点(把Lys突变为Leu)并不能获得对胰凝乳蛋白酶的抑制活性,这表明RBBI3-1的D1结构域反应回环阻碍了P1位点获得新的抑制活性;而对胰凝乳蛋白酶的抑制活性可能还需要其他结构(比如3:13二硫键)的参与.
Rice Bowman-Birk protease inhibitor (RBBI) is a trypsin inhibitor in vitro, some have one homologous domain (8kD), some have two homologous domains (16kD) .This study found that in rice RBBI with three homology domains (25 kD) is present in vivo and RBBI is regulated by development and injury In vitro experiments showed that 3: 13 disulfide bonds (but not 4: 5 disulfide bonds) inhibited trypsin activity , While the D3 domain of RBBI3-1 had no inhibitory activity on trypsin, chymotrypsin, papain and bacillus subtilis.Mutation experiments showed that changing the P1 site at the N-terminal of the D1 domain (changing Lys to Leu) The inability to obtain the inhibitory activity on chymotrypsin suggests that the loopback of the D1 domain of RBBI3-1 hinders the attainment of a new inhibitory activity at the P1 site; whereas the inhibitory activity on chymotrypsin may require additional structures (eg, 3 : 13 disulfide bond).