The crystal structure of human protein farnesyltransferase reveals the basis for inhibition by CaaX tetrapeptides and their mimetics
The crystal structure of human protein farnesyltransferase reveals the basis for inhibition by CaaX tetrapeptides and their mimetics
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DOI：
10.1073/pnas.241407898
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发表时间：
2001-11-06
影响因子：
11.1
通讯作者：
Beese, LS
中科院分区：
文献类型：
--
作者：
Long, SB;Hancock, PJ;Beese, LS
蛋白法尼基转移酶（FTase）催化法尼基脂质基团与位于许多必需信号转导蛋白（包括Ras超家族成员）的C-末端四肽中的半胱氨酸残基的连接。法尼基化对于这些蛋白质的正常功能和致癌突变体的转化活性都是必需的。因此，FTase是抗癌治疗的重要靶标。几种FTase抑制剂目前正在进行癌症治疗的临床试验。在这里，我们提出了人FTase的晶体结构，以及与TKCVFM六肽底物，CVFM非底物四肽，L-739，750肽模拟物与法呢基二磷酸（FPP），或非反应性类似物的三元复合物。这些结构揭示了FTase抑制的结构机制。一些CaaX四肽抑制剂不是法尼基化的，并且是比法尼基化的CaaX四肽更有效的抑制剂。CVFM和L-739，750未被法尼基化，因为这些抑制剂以不同于TKCVFM六肽底物的构象结合。这种非底物结合模式通过肽N末端和FPP底物的α-磷酸之间的离子对来稳定。构象映射计算揭示了CaaX基序的第三位置的序列特异性的基础，该基序决定了四肽是底物还是非底物。该位置中β-支链氨基酸的存在防止了非底物构象的形成;预测该位置中的所有其他脂肪族氨基酸形成非底物构象，前提是它们的N末端可用于结合FPP α-磷酸。这些结果可能有助于FTase抑制剂的进一步开发。
Protein farnesyltransferase (FTase) catalyzes the attachment of a farnesyl lipid group to the cysteine residue located in the C-terminal tetrapeptide of many essential signal transduction proteins, including members of the Ras superfamily. Farnesylation is essential both for normal functioning of these proteins, and for the transforming activity of oncogenic mutants. Consequently FTase is an important target for anti-cancer therapeutics. Several FTase inhibitors are currently undergoing clinical trials for cancer treatment. Here, we present the crystal structure of human FTase, as well as ternary complexes with the TKCVFM hexapeptide substrate, CVFM non-substrate tetrapeptide, and L-739,750 peptidomimetic with either farnesyl diphosphate (FPP), or a nonreactive analogue. These structures reveal the structural mechanism of FTase inhibition. Some CaaX tetrapeptide inhibitors are not farnesylated, and are more effective inhibitors than farnesylated CaaX tetrapeptides. CVFM and L-739,750 are not farnesylated, because these inhibitors bind in a conformation that is distinct from the TKCVFM hexapeptide substrate. This non-substrate binding mode is stabilized by an ion pair between the peptide N terminus and the alpha-phosphate of the FPP substrate. Conformational mapping calculations reveal the basis for the sequence specificity in the third position of the CaaX motif that determines whether a tetrapeptide is a substrate or non-substrate. The presence of beta-branched amino acids in this position prevents formation of the non-substrate conformation; all other aliphatic amino acids in this position are predicted to form the non-substrate conformation, provided their N terminus is available to bind to the FPP alpha-phosphate. These results may facilitate further development of FTase inhibitors.