Sekine T, Takahashi S, Hikita S, Sutoh N, Satake K
J Biochem. 1984 Jul;96(1):27-33. doi: 10.1093/oxfordjournals.jbchem.a134824.
Myosin has 2 mol of the most reactive thiol, named SH1. 1,2,4-Trinitrobenzene (TNB), a novel dinitrophenyl(DNP)ating reagent [Takahashi et al. (1983) Chem. Lett. 1445-1448], was found to react only with SH1 without any other amino acid residues in myosin under the conditions used. Its reaction with myosin SH1 was about 30 times faster than that with N-acetylcysteine (NAC). The reaction rate of TNB with SH1 was about twice compared with that of NEM, the most reactive selective reagent for SH1 so far found, although its rate with NAC was only one sixtieth that of NEM. As to the lambda max of the absorption spectrum of SH1-DNP-myosin, a large red shift of as much as 20 nm was observed compared with low molecular S-DNP derivatives. This red shift disappeared in 8 M urea. This outstanding feature of SH1 modification with TNB was discussed in terms of affinity labeling by interaction with an aromatic amino acid near SH1.
肌球蛋白含有2摩尔反应活性最高的巯基，称为SH1。1,2,4-三硝基苯（TNB）是一种新型二硝基苯基（DNP）化试剂[高桥等人（1983年），《化学通讯》，第1445 - 1448页]，发现在所用条件下，它仅与肌球蛋白中的SH1反应，而不与任何其他氨基酸残基反应。它与肌球蛋白SH1的反应速度比与N - 乙酰半胱氨酸（NAC）的反应速度快约30倍。TNB与SH1的反应速率与N - 乙基马来酰亚胺（NEM，迄今为止发现的对SH1反应活性最高的选择性试剂）相比约为两倍，尽管它与NAC的反应速率仅为NEM的六十分之一。关于SH1 - DNP - 肌球蛋白吸收光谱的最大吸收波长（λmax），与低分子S - DNP衍生物相比，观察到高达20 nm的大红移。这种红移在8 M尿素中消失。根据与SH1附近芳香族氨基酸相互作用的亲和标记，讨论了用TNB修饰SH1的这一突出特性。
