Wang C C, Tsou C L
Biochemistry. 1986 Sep 9;25(18):5336-40. doi: 10.1021/bi00366a052.
With the S-(thiomethyl)-A chain and despentapeptide (26-30) and desoctapeptide (23-30) S-(thiomethyl)-B chains of insulin at pH 10.8 and a molar ratio of A/B = 1.5, difference spectra of the mixed against the separated chains with negative peaks at 245 and 295 nm and a weak positive peak at 278 nm indicate interaction of the chains leading to Tyr environmental changes as in the case for the intact chains. With the shortened B chains, freshly dissolved from lyophilized powders, it takes some 2 h for the difference spectra to approach completion whereas with the solutions of the shortened B chains left standing overnight at pH 10.8 and 4 degrees C the difference spectra, similar in shape to that described above, appear almost immediately after mixing. Solvent perturbation with 20% ethylene glycol suggests some ordered structure for the despentapeptide but not for the desoctapeptide B chain. The interactions of the A chain with the shortened B chains appear to be weaker as compared to that with the intact B chain as shown by decreasing reconstitution yields for the intact, despentapeptide, and desoctapeptide B chains respectively with the A chain. The above results indicate that the C-terminal portion of the B chain is important not only for the activity of insulin but also for the correct pairing of the chains.
在pH 10.8、A/B摩尔比为1.5的条件下，将胰岛素的S-（硫甲基）-A链与去五肽（26 - 30）和去八肽（23 - 30）S-（硫甲基）-B链混合，混合链与分离链的差示光谱在245和295 nm处有负峰，在278 nm处有一个弱正峰，这表明链间相互作用导致酪氨酸环境发生变化，如同完整链的情况。对于从冻干粉末中新鲜溶解的缩短B链，差示光谱达到完全需要约2小时，而将缩短B链的溶液在pH 10.8和4℃下放置过夜，混合后差示光谱几乎立即出现，其形状与上述相似。用20%乙二醇进行溶剂扰动表明去五肽B链有一些有序结构，但去八肽B链没有。与完整B链相比，A链与缩短B链的相互作用似乎较弱，这分别通过完整、去五肽和去八肽B链与A链重构产率的降低得以体现。上述结果表明，B链的C末端部分不仅对胰岛素的活性很重要，而且对链的正确配对也很重要。
