Nielsen K J, Heath R L, Anderson M A, Craik D J
Victorian College of Pharmacy, Monash University, Parkville, Australia.
J Mol Biol. 1994 Sep 23;242(3):231-43. doi: 10.1006/jmbi.1994.1575.
The three-dimensional structure and disulfide connectivities of a 6-kDa protein isolated from the stigma of the ornamental tobacco Nicotiana alata has been determined by 1H NMR spectroscopy combined with simulated annealing calculations. The protein, termed C1, is a chymotrypsin inhibitor and is one of five homologous proteinase inhibitors that are proteolytically cleaved from a 40.3-kDa precursor protein. The other four proteinase inhibitors (T1 to T4) contain reactive sites for trypsin. The three-dimensional structure of C1 is generally well defined and contains a triple stranded beta-sheet as the dominant secondary structural feature. Several turns and a short region of 3(10) helix are also present. The putative chymotrypsin reactive site is present on an exposed loop which is less defined than the rest of the protein. The overall shape of C1 is disc-like and the N and C termini are exposed, supporting the proposal that this protein results from post-translational processing of the 40.3-kDa precursor protein.
通过结合模拟退火计算的1H NMR光谱法，已确定了从观赏烟草烟草属植物的柱头中分离出的一种6 kDa蛋白质的三维结构和二硫键连接性。该蛋白质称为C1，是一种胰凝乳蛋白酶抑制剂，是从40.3 kDa前体蛋白经蛋白水解切割产生的五种同源蛋白酶抑制剂之一。其他四种蛋白酶抑制剂（T1至T4）含有针对胰蛋白酶的反应位点。C1的三维结构总体上定义明确，包含一个三链β-折叠作为主要的二级结构特征。还存在几个转角和一小段3(10)螺旋区域。假定的胰凝乳蛋白酶反应位点位于一个暴露的环上，该环的定义不如蛋白质的其余部分明确。C1的整体形状呈盘状，N端和C端暴露在外，这支持了该蛋白质是由40.3 kDa前体蛋白经翻译后加工产生的这一观点。
