Cocrystal structure of protein farnesyltransferase complexed with a farnesyl diphosphate substrate
Cocrystal structure of protein farnesyltransferase complexed with a farnesyl diphosphate substrate
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DOI：
10.1021/bi980708e
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发表时间：
1998-07-07
期刊：
影响因子：
2.9
通讯作者：
Beese, LS
中科院分区：
文献类型：
--
作者：
Long, SB;Casey, PJ;Beese, LS
蛋白法尼基转移酶（FTase）催化疏水性法尼基基团从法尼基二磷酸（FPP）转移到细胞蛋白（如Pas），其羧基端附近的半胱氨酸残基。这一过程对于这些蛋白的亚细胞定位到质膜是必要的，也是Pas致癌变异体转化活性所必需的，这使得FTase成为抗癌治疗的主要靶点。大鼠FTase的高分辨率晶体结构最近被确定，我们在这里展示了在活性位点结合FPP底物的FTase的第一个复合物的x射线晶体结构。FPP的类异丙二烯部分以延伸的构象结合在FTase β亚基的疏水腔中，二磷酸部分结合在该腔顶部靠近亚基界面的带正电的间隙上。观察到的FPP分子位置与诱变数据一致。这种FTase与FPP的二元复合物使我们提出了一种类异戊二烯底物特异性的“分子标尺”假设，其中疏水结合腔的深度作为区分不同长度的类异戊二烯的标尺。虽然其他长度的类异戊二烯也可以在腔中结合，但只有15碳的法尼基部分与它的Cl原子结合，并与催化锌离子结合，以有效地转移到Ras底物。
Protein farnesyltransferase (FTase) catalyzes the transfer of the hydrophobic farnesyl group from farnesyl diphosphate (FPP) to cellular proteins such as Pas at a cysteine residue near their carboxy-terminus. This process is necessary for the subcellular localization of these proteins to the plasma membrane and is required for the transforming activity of oncogenic variants of Pas, making FTase a prime target for anticancer therapeutics. The high-resolution crystal structure of rat FTase was recently determined, and we present here the X-ray crystal structure of the first complex of FTase with a FPP substrate bound at the active site. The isoprenoid moiety of FPP binds in an extended conformation in a hydrophobic cavity of the beta subunit of the FTase enzyme, and the diphosphate moiety binds to a positively charged cleft at the top of this cavity near the subunit interface. The observed location of the FPP molecule is consistent with mutagenesis data. This binary complex of FTase with FPP leads us to suggest a "molecular ruler" hypothesis for isoprenoid substrate specificity, where the depth of the hydrophobic binding cavity acts as a ruler discriminating between isoprenoids of differing lengths. Although other length isoprenoids may bind in the cavity, only the 15-carbon farnesyl moiety binds with its Cl atom in register with a catalytic zinc ion as required for efficient transfer to the Ras substrate.