Tian Y, Wang C C, Tsou C L
Biol Chem Hoppe Seyler. 1987 Apr;368(4):397-403. doi: 10.1515/bchm3.1987.368.1.397.
The S-thiomethyl derivatives of insulin A chain with A1-Gly replaced by D- or L-Trp have been prepared and their respective interaction and combination with the S-thiomethyl B chain studied. The UV difference spectra of the mixed against the separated [Trp1]A chains with the B chain at pH 10.8 are similar to those obtained for the unmodified chains except that the 295-nm-negative peak for ionized Tyr residue appears to be less marked. Fluorescence studies show very little environmental changes at the A1-Trp residues when mixed with the B chain. The intact hormone with A1-Gly replaced by D-Trp is known to be considerably more active than the analog with L-Trp replacement. However, for both derivatives the resynthesis of the whole molecules correctly joined by disulfide bridges starting from the separated reduced chains, gives similar low yields as shown by HPLC analysis and by receptor-binding assay. The replacement of A1-Gly by D-Trp appears to affect the separated A chain more than the intact hormone and replacements at A1 by both D- and L-Trp probably lead to significant conformational changes of the A chain so as to prevent its correct pairing with the B chain.
已制备了胰岛素A链中A1 - Gly被D - 或L - Trp取代的S - 硫甲基衍生物，并研究了它们与S - 硫甲基B链各自的相互作用和结合情况。在pH 10.8下，将混合的[Trp1]A链与B链的紫外差光谱与分离的[Trp1]A链的紫外差光谱进行比较，结果与未修饰链的紫外差光谱相似，只是离子化的Tyr残基的295 - nm负峰似乎不太明显。荧光研究表明，与B链混合时，A1 - Trp残基处的环境变化非常小。已知A1 - Gly被D - Trp取代的完整激素比被L - Trp取代的类似物活性高得多。然而，对于这两种衍生物，从分离的还原链开始通过二硫键正确连接合成的完整分子，经高效液相色谱分析和受体结合试验表明，产率都很低。A1 - Gly被D - Trp取代似乎对分离的A链的影响比对完整激素的影响更大，A1被D - 和L - Trp取代可能导致A链发生显著的构象变化，从而阻止其与B链正确配对。
