Jerala R, Kroon-Zitko L, Kopitar M, Popovic T, Turk V
Department of Biochemistry, Jozef Stefan Institute, Ljubljana, Yugoslavia.
Biomed Biochim Acta. 1991;50(4-6):627-9.
Determination of crystal structures of chicken cystatin and human stefin B complexed with papain revealed a novel model of protease inhibition and also structural differences between two cysteine proteinase inhibitor (CPI) families. According to the 3D alignment, stefins have an extension of 9 amino acids on their carboxy terminus in comparison with cystatins. The extension was not expected to make a major contribution to interaction with the enzyme. A deletion mutant of stefin B, corresponding in length to the carboxy terminal sequence of chicken cystatin, was constructed by the use of polymerase chain reaction (PCR). This (C3S, delta 89-98) human stefin B, 10 amino acids shorter, inhibited papain with a Ki of 0.012 nM which is comparable to the Ki of 0.03 nM for authentic, nondeleted recombinant stefin B. This finding thus confirms the tertiary structure-based alignment.
鸡半胱氨酸蛋白酶抑制剂与木瓜蛋白酶复合的人丝氨酸蛋白酶抑制剂B晶体结构的测定揭示了一种新型蛋白酶抑制模型以及两个半胱氨酸蛋白酶抑制剂（CPI）家族之间的结构差异。根据三维比对，与半胱氨酸蛋白酶抑制剂相比，丝氨酸蛋白酶抑制剂在其羧基末端有9个氨基酸的延伸。预计该延伸对与酶的相互作用不会有主要贡献。通过使用聚合酶链反应（PCR）构建了与人丝氨酸蛋白酶抑制剂B的羧基末端序列长度相对应的缺失突变体。这种（C3S，δ89 - 98）人丝氨酸蛋白酶抑制剂B短10个氨基酸，以0.012 nM的Ki抑制木瓜蛋白酶，这与未缺失的重组人丝氨酸蛋白酶抑制剂B的0.03 nM的Ki相当。因此，这一发现证实了基于三级结构的比对。
