Kuramitsu S, Hamaguchi K, Tachibana H, Horii T, Ogawa T, Ogawa H
Biochemistry. 1984 May 22;23(11):2363-7. doi: 10.1021/bi00306a006.
The Escherichia coli recA protein has three cysteinyl residues at positions 90, 116, and 129. All of them are reactive with 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB). In the presence of ATP or ADP, only one cysteinyl residue reacts with DTNB. The residue was also reactive with N-[7-(dimethylamino)-4-methylcoumarinyl]maleimide (DACM) in the presence of ATP. The results on an analysis of the DACM-modified protein cleaved at the nonmodified cysteinyl residues after cyanation with 2-nitro-5-(thiocyano)benzoic acid show that two cysteinyl residues protected in the presence of ATP or ADP are identified as Cys-90 and Cys-129. When the ionic strength is higher than 1, one cysteinyl residue does not react with DTNB. This residue is Cys-90 or Cys-129, because one of the two cysteinyl residues, which are not modified with DACM in the presence of ATP, does not react with DTNB at high ionic strength. The binding of single-stranded DNA to the recA protein does not change the reactivity of the cysteinyl residues with DTNB.
大肠杆菌RecA蛋白在第90、116和129位有三个半胱氨酰残基。它们都能与5,5'-二硫代双（2-硝基苯甲酸）（DTNB）发生反应。在ATP或ADP存在的情况下，只有一个半胱氨酰残基与DTNB反应。在ATP存在的情况下，该残基也能与N-[7-（二甲基氨基）-4-甲基香豆素基]马来酰亚胺（DACM）发生反应。在用2-硝基-5-（硫氰基）苯甲酸氰化后，对在未修饰的半胱氨酰残基处裂解的DACM修饰蛋白的分析结果表明，在ATP或ADP存在下受到保护的两个半胱氨酰残基被鉴定为Cys-90和Cys-129。当离子强度高于1时，有一个半胱氨酰残基不与DTNB反应。这个残基是Cys-90或Cys-129，因为在ATP存在下未被DACM修饰的两个半胱氨酰残基中的一个在高离子强度下不与DTNB反应。单链DNA与RecA蛋白的结合不会改变半胱氨酰残基与DTNB的反应性。
