Thomassen Ellen A J, Pouvreau Laurice, Gruppen Harry, Abrahams Jan Pieter
Biophysical Structural Chemistry, Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC, The Netherlands.
Acta Crystallogr D Biol Crystallogr. 2004 Aug;60(Pt 8):1464-6. doi: 10.1107/S0907444904013484. Epub 2004 Jul 21.
Interest in protease inhibitors has been renewed because of their potent activity in preventing carcinogenesis in a wide variety of in vivo and in vitro model systems. Potato tubers contain a wide range of such protease inhibitors. In cv. Elkana potato tubers, protease inhibitors represent about 50% of the total amount of soluble protein. Potato serine protease inhibitor (PSPI), one of the isoforms of the most abundant group of protease inhibitors, is a dimeric double-headed Kunitz-type inhibitor. No high-resolution structural information on this type of inhibitor has so far been obtained, as all currently known structures are of the monomeric single-headed or monomeric double-headed types. Crystals were grown in 0.1 M HEPES pH 7.5, 10% PEG 8000 and 8% ethylene glycol complemented with 9 mM 1-s-octyl-beta-D-thioglucoside or 0.1 M glycine. Data were collected from a single crystal under cryoconditions to 1.8 A resolution. The protein crystallized in space group P2(1), with unit-cell parameters a = 54.82, b = 93.92, c = 55.44 A, beta = 100.7 degrees; the scaling Rsym is 0.044 for 45,456 unique reflections.
由于蛋白酶抑制剂在多种体内和体外模型系统中预防致癌作用的强大活性，人们对其兴趣再度燃起。马铃薯块茎含有多种此类蛋白酶抑制剂。在埃尔卡纳品种的马铃薯块茎中，蛋白酶抑制剂约占可溶性蛋白质总量的50%。马铃薯丝氨酸蛋白酶抑制剂（PSPI）是最丰富的蛋白酶抑制剂组的同工型之一，是一种二聚体双头库尼茨型抑制剂。到目前为止，尚未获得关于此类抑制剂的高分辨率结构信息，因为目前所有已知结构均为单体单头或单体双头类型。晶体在0.1 M HEPES pH 7.5、10%聚乙二醇8000和8%乙二醇中生长，并添加9 mM 1 - s - 辛基 - β - D - 硫代葡萄糖苷或0.1 M甘氨酸。在低温条件下从单个晶体收集数据，分辨率达到1.8 Å。该蛋白质在空间群P2(1)中结晶，晶胞参数为a = 54.82、b = 93.92、c = 55.44 Å，β = 100.7°；对于45,456个独立反射，标度Rsym为0.044。
