Prasad A R, Luduena R F
Biochem Int. 1987 Jan;14(1):85-93.
Bovine brain tubulin purified in the absence of GTP and MgCl2, reacts with 5'-p-fluorosulfonylbenzoylguanosine (5'-FSBG)2, an affinity analog of GTP and two moles of the reagent are incorporated per mole of tubulin at 0 degree C. 5'-FSBG is unable to promote the polymerization of tubulin into microtubules. 2 mM GTP, podophyllotoxin and vinblastine provide almost 50% protection against the modification, when added individually. Combination of these ligands gives maximal protection. Tubulin modified with 5'-FSBG lost two sulfhydryl groups per mole of tubulin and reduction with beta-mercaptoethanol led to the loss of the 2 moles of FSBG that had been incorporated. These data are interpreted on the basis that the modification of tubulin by 5'-FSBG proceeds via a thiosulfonate intermediate between the analogue and a reactive thiol group at or near that portion of the GTP binding site of tubulin where the phosphate moiety of GTP binds.
在没有鸟苷三磷酸（GTP）和氯化镁（MgCl2）的情况下纯化的牛脑微管蛋白，与5'-对氟磺酰苯甲酰鸟苷（5'-FSBG）发生反应，5'-FSBG是GTP的一种亲和类似物，在0摄氏度时，每摩尔微管蛋白会掺入两摩尔该试剂。5'-FSBG无法促进微管蛋白聚合成微管。单独添加2 mM GTP、鬼臼毒素和长春花碱时，可提供近50%的修饰保护作用。这些配体组合可提供最大程度的保护。用5'-FSBG修饰的微管蛋白每摩尔微管蛋白失去两个巯基，用β-巯基乙醇还原会导致已掺入的两摩尔FSBG丢失。这些数据的解释依据是，5'-FSBG对微管蛋白的修饰是通过该类似物与微管蛋白GTP结合位点处或附近与GTP磷酸基团结合的反应性巯基之间的硫代磺酸盐中间体进行的。
