Krauchenco Sandra, Pando Silvana C, Marangoni Sérgio, Polikarpov Igor
Instituto de Física de São Carlos, USP, Av. Trabalhador Saocarlense, 400, CEP 13560-970, São Carlos, SP, Brazil.
Biochem Biophys Res Commun. 2003 Dec 26;312(4):1303-8. doi: 10.1016/j.bbrc.2003.11.062.
The three-dimensional structure of a novel Kunitz (STI) family member, an inhibitor purified from Delonix regia seeds (DrTI), was solved by molecular replacement method and refined, respectively, to R(factor) and R(free) values of 21.5% and 25.3% at 1.75A resolution. The structure has a classical beta-trefoil fold, however, differently from canonical Kunitz type (STI) inhibitors, its reactive site loop has an insertion of one residue, Glu68, between the residues P1 and P2. Surprisingly, DrTI is an effective inhibitor of trypsin and human plasma kallikrein, but not of chymotrypsin and tissue kallikrein. Putative structural grounds of such specificity are discussed.
从凤凰木种子中纯化得到的一种新型库尼茨（大豆胰蛋白酶抑制剂，STI）家族成员抑制剂（DrTI），通过分子置换法解析了其三维结构，并分别在1.75埃分辨率下精修至R（因子）和R（游离）值为21.5%和25.3%。该结构具有经典的β-三叶折叠，但与典型的库尼茨型（STI）抑制剂不同的是，其反应位点环在P1和P2残基之间插入了一个残基Glu68。令人惊讶的是，DrTI是胰蛋白酶和人血浆激肽释放酶的有效抑制剂，但不是胰凝乳蛋白酶和组织激肽释放酶的抑制剂。文中讨论了这种特异性的假定结构基础。
