Parente A, Branno M, Malorni M C, Welling G W, Libonati M, D'Alessio G
Biochim Biophys Acta. 1976 Sep 14;445(2):377-85. doi: 10.1016/0005-2744(76)90091-7.
Trypsin, pepsin and subtilisin have been used as conformational probes for the structure of bovine seminal ribonuclease BS-1 by studying, under definite conditions, their effects on the seminal enzyme, a dimeric protein made up to two identical subunits; on bovine pancreatic monomeric ribonuclease A (EC 3.1.4.22) with a polypeptide chain homologous to that of the seminal ribonuclease subunit chain; and on a monomeric, active and stable derivative of seminal ribonuclease. The results show: (1) that the C-terminal regions of the pancreatic and the seminal proteins are very similar as they appear to fit in an identical way to the active site of pepsin; (2) that the resistance of the N-terminal region of ribonuclease BS-1 to subtilisin is not due to the dimeric structure of the protein, but to the conformation of this region, where an essential feature is the presence of a proline residue at position 19; (3) that the monomer of ribonuclease BS-1 is resistant to tryptic action only when bound to the partner monomer in the quaternary structure of the protein. This indicates that dissociation of the seminal ribonuclease makes some potentially susceptible susceptible bond or bonds available to trypsin either through a conformational change of the protein subunit, or by simply exposing the protein area hidden at the intersubunit interfaces.
通过在特定条件下研究胰蛋白酶、胃蛋白酶和枯草杆菌蛋白酶对牛精液核糖核酸酶BS - 1结构的影响，它们被用作构象探针。牛精液核糖核酸酶BS - 1是一种由两个相同亚基组成的二聚体蛋白质；还研究了它们对牛胰单体核糖核酸酶A（EC 3.1.4.22）的影响，该酶的多肽链与精液核糖核酸酶亚基链同源；以及对精液核糖核酸酶的一种单体、活性且稳定的衍生物的影响。结果表明：（1）胰脏和精液蛋白质的C末端区域非常相似，因为它们似乎以相同的方式契合胃蛋白酶的活性位点；（2）核糖核酸酶BS - 1的N末端区域对枯草杆菌蛋白酶的抗性并非由于蛋白质的二聚体结构，而是由于该区域的构象，其一个基本特征是在第19位存在一个脯氨酸残基；（3）核糖核酸酶BS - 1的单体仅在与蛋白质四级结构中的伙伴单体结合时才对胰蛋白酶作用具有抗性。这表明精液核糖核酸酶的解离通过蛋白质亚基的构象变化，或者仅仅通过暴露隐藏在亚基间界面处的蛋白质区域，使一些潜在的易感键对胰蛋白酶可用。
