Synthesis of high specific activity 35S-labelled N-methanesulfonyl farnesylcysteine and a photoactive analog
作者:Tamara A. Kale、Conrad Raab、Nathan Yu、Evelyn Aquino、Dennis C. Dean、Mark D. Distefano
DOI:10.1002/jlcr.638
日期:2003.1
Prenylated cysteine analogs, which mimic the prenylated cysteine residue of prenylated GTP-binding proteins (G-proteins), have been used in a variety of contexts for the study of prenylated G-protein behavior. In earlier work in this area, we prepared the photoactive analog [35S]4 and showed that it labelled RhoGDI upon photolysis; those results were consistent with the idea that GDI contains an isoprenoid binding site. Here, we describe the preparation of [35S]N-methanesulfonyl labelled analogs (1a and 2a) of N-acetyl farnesylcysteine and its methyl ester together with an improved synthetic procedure for photoactive analogs 3 and 4; specific activities of ∼1100 Ci/mmol were achieved. Compounds 1a and 2a in unlabelled form were used as competitors in photolysis reactions to show that the methanesulfonamido group is a reasonable acetamide substitution. Additional experiments show that the photoactive ester [35S]3 can cross-link GDI in both purified form and crude bacterial extract. However, the extent of cross-linking obtained with the ester ([35S]3) is significantly less than that observed with the free acid ([35S]4) despite the fact that the esterified form probably more closely reflects the structure of the C-terminus of a prenylated protein; using the GDI·Cdc42 co-crystal structure, the structural basis for these results is discussed. Copyright © 2002 John Wiley & Sons, Ltd.
前烯丙基化半胱氨酸类似物模拟前烯丙基化 GTP 结合蛋白(G 蛋白)的前烯丙基化半胱氨酸残基,已被广泛用于研究前烯丙基化 G 蛋白的行为。在这一领域的早期研究中,我们制备了光活性类似物 [35S]4,并证明它能在光解时标记 RhoGDI;这些结果与 GDI 包含异肾上腺素结合位点的观点一致。在此,我们介绍了 N-乙酰法尼基半胱氨酸及其甲酯的[35S]N-甲磺酰基标记类似物(1a 和 2a)的制备过程,以及光活性类似物 3 和 4 的改进合成过程;其比活性达到了 1100 Ci/mmol。未标记的化合物 1a 和 2a 被用作光解反应的竞争者,表明甲磺酰胺基是一种合理的乙酰胺取代基。其他实验表明,光活性酯 [35S]3 可以交联纯化形式和粗细菌提取物中的 GDI。然而,使用酯([35S]3)获得的交联程度明显低于使用游离酸([35S]4)观察到的交联程度,尽管酯化形式可能更接近于反映前炔化蛋白质 C 端的结构;使用 GDI-Cdc42 共晶体结构,讨论了这些结果的结构基础。Copyright © 2002 John Wiley & Sons, Ltd. All Rights Reserved.