Nilsson T, Sjöholm I, Wiman B
Biochem J. 1983 Sep 1;213(3):617-24. doi: 10.1042/bj2130617.
The reaction between complement factor C1s and C1-esterase inhibitor has been investigated by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, N-terminal amino acid analysis and c.d. studies. It is confirmed that a very stable stoichiometric 1:1 complex with a molecular weight of about 180000 is formed, involving the light chain of C1s. On the sodium dodecyl sulphate/polyacrylamide gels a small peptide with a molecular weight of about 5000 can be seen, which may be released from the C-terminal portion of the inhibitor moiety in a manner analogous to that occurring in other similar proteinase-inhibitor reactions. By N-terminal amino acid analysis, a newly formed threonine residue is found in the complex, suggesting that the inhibitor peptide chain is cleaved in the complex between C1s and C1-esterase inhibitor. The stabilizing bond may therefore be an ester bond. C.d. studies of the native C1-esterase inhibitor indicated the presence of about 38% alpha-helix, about 24% beta-structure and about 38% unordered structure. By gradual cleavage of the disulphide bridges under non-denaturating conditions, gradual changes in the c.d. spectra occurred, suggesting loss of ordered secondary structures. The c.d. spectra of the complex between C1s and C1-esterase inhibitor indicate that tryptophan residues are affected by the complex-formation.
通过十二烷基硫酸钠/聚丙烯酰胺凝胶电泳、N端氨基酸分析和圆二色性研究，对补体因子C1s与C1酯酶抑制剂之间的反应进行了研究。已证实形成了一种非常稳定的化学计量比为1:1的复合物，其分子量约为180000，涉及C1s的轻链。在十二烷基硫酸钠/聚丙烯酰胺凝胶上可以看到一种分子量约为5000的小肽，它可能以类似于其他类似蛋白酶-抑制剂反应中发生的方式从抑制剂部分的C端释放出来。通过N端氨基酸分析，在复合物中发现了一个新形成的苏氨酸残基，这表明抑制剂肽链在C1s和C1酯酶抑制剂之间的复合物中被切割。因此，稳定键可能是酯键。天然C1酯酶抑制剂的圆二色性研究表明，其存在约38%的α螺旋、约24%的β结构和约38%的无规结构。在非变性条件下通过逐步切割二硫键，圆二色光谱发生了逐步变化，表明有序二级结构的丧失。C1s与C1酯酶抑制剂之间复合物的圆二色光谱表明，色氨酸残基受复合物形成的影响。
