Puigserver A, Desnuelle P
Biochemistry. 1977 May 31;16(11):2497-501. doi: 10.1021/bi00630a028.
The three subunits I, II, and III of bovine procarboxypeptidase A separated by reversible dimethylmaleylation can reassociate to form the reconstituted complexes I + II, I + III, and I + II + III. Since the association II + III is not possible, subunit I appears to play a central role in the formation of the complex. It is suggested that subunit I possesses two independent and specific sites for the recognition of subunits II and III. The liberation of subunit I from any of the complexes was observed to increase its activability, although to a lesser extent than predicted by assays carried out with the succinylated protein. By contrast, the bound form of subunit II was activated faster than the free form. The potential activity of the bound form and the activity of the preformed endopentidase were also higher, suggesting a conformational change induced by association. This suggestion was fully supported by the observed modifications of the heat stability and intrinsic fluorescence spectrum of the subunit resulting form association.
通过可逆的二甲基马来酰化分离得到的牛羧肽酶原A的三个亚基I、II和III可以重新结合形成重组复合物I + II、I + III和I + II + III。由于II + III的结合不可能发生，亚基I似乎在复合物的形成中起核心作用。有人提出亚基I拥有两个独立且特异的位点来识别亚基II和III。观察到从任何一种复合物中释放出亚基I都会增加其可激活性，尽管程度小于用琥珀酰化蛋白进行的测定所预测的程度。相比之下，亚基II的结合形式比游离形式激活得更快。结合形式的潜在活性和预先形成的内肽酶的活性也更高，表明结合诱导了构象变化。结合所导致的亚基热稳定性和内在荧光光谱的观察到的变化充分支持了这一观点。
