Dolence J M, Poulter C D
Department of Chemistry, University of Utah, Salt Lake City 84112, USA.
Proc Natl Acad Sci U S A. 1995 May 23;92(11):5008-11. doi: 10.1073/pnas.92.11.5008.
Protein farnesyltransferase catalyzes the alkylation of cysteine in C-terminal CaaX sequences of a variety of proteins, including Ras, nuclear lamins, large G proteins, and phosphodiesterases, by farnesyl diphosphate (FPP). These modifications enhance the ability of the proteins to associate with membranes and are essential for their respective functions. The enzyme-catalyzed reaction was studied by using a series of substrate analogs for FPP to distinguish between electrophilic and nucleophilic mechanisms for prenyl transfer. FPP analogs containing hydrogen, fluoromethyl, and trifluoromethyl substituents in place of the methyl at carbon 3 were evaluated as alternative substrates for alkylation of the sulfhydryl moiety in the peptide dansyl-GCVIA. The analogs were alternative substrates for the prenylation reaction and were competitive inhibitors against FPP. A comparison of kcat for FPP and the analogs with ksolv, the rate constants for solvolysis of related p-methoxybenzenesulfonate derivatives, indicated that protein prenylation occurred by an electrophilic mechanism.
蛋白质法尼基转移酶催化法尼基二磷酸（FPP）对多种蛋白质（包括Ras、核纤层蛋白、大G蛋白和磷酸二酯酶）C末端CaaX序列中的半胱氨酸进行烷基化。这些修饰增强了蛋白质与膜结合的能力，对其各自的功能至关重要。通过使用一系列FPP的底物类似物研究酶催化反应，以区分亲电和亲核的异戊二烯基转移机制。评估了在碳3处含有氢、氟甲基和三氟甲基取代基以替代甲基的FPP类似物作为肽丹磺酰-GCVIA中巯基部分烷基化的替代底物。这些类似物是异戊二烯基化反应的替代底物，并且是FPP的竞争性抑制剂。将FPP及其类似物的kcat与相关对甲氧基苯磺酸酯衍生物的溶剂解速率常数ksolv进行比较，表明蛋白质异戊二烯基化是通过亲电机制发生的。
