A second mammalian N-myristoyltransferase
A second mammalian N-myristoyltransferase
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DOI：
10.1074/jbc.273.12.6595
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发表时间：
1998-03-20
影响因子：
4.8
通讯作者：
Cravatt, BF
中科院分区：
文献类型：
--
作者：
Giang, DG;Cravatt, BF
N-末端豆蔻酰化是许多信号蛋白共同的共翻译脂质修饰，其通常在这些蛋白的靶向和/或功能中起不可或缺的作用。肉豆蔻酰化由酶活性N-肉豆蔻酰转移酶（NMT）催化，其将肉豆蔻酸从肉豆蔻酰辅酶A转移到蛋白质的N-末端甘氨酸残基的氨基。虽然一个单一的人NMT cDNA已被分离和表征（hNMT-1），生化证据表明，在体内存在几个不同的NMT，往往在表观分子量和/或亚细胞分布不同。我们现在报告的克隆和表征的第二个，遗传上不同的人类NMT（hNMT-2），以及各自的小鼠NMT同源物的分离每个人的酶。每种NMT的小鼠和人版本高度同源，显示大于95%的氨基酸序列同一性。NMT-1和NMT-2蛋白质之间的比较揭示了降低的序列同一性水平（76-77%），表明NMT-1和NMT-2包含两个不同的N-肉豆蔻酰转移酶家族。将hNMT-1或hNMT-2 cDNA瞬时转染到COS-7细胞中导致高水平的NMT酶活性的表达。发现hNMT-1和hNMT-2都以相似但可区分的相对选择性将几种通常研究的肽底物肉豆蔻酰化。Western分析显示，虽然hNMT-2在转染的COS-7细胞中表现为单一的65 kDa蛋白，但hNMT-1被加工成大小从49至68 kDa的四种不同的蛋白异构体。总的来说，这些研究表明了迄今为止未被认识到的N-末端豆蔻酰化酶学基础的遗传复杂性水平，并表明体内NMT的特异性抑制或调节反过来可以允许选择性控制特定的豆蔻酰化依赖性细胞功能。
N-terminal myristoylation is a cotranslational lipid modification common to many signaling proteins that often serves an integral role in the targeting and/or function of these proteins. Myristoylation is catalyzed by an enzyme activity, N-myristoyltransferase (NMT), which transfers myristic acid from myristoyl coenzyme A to the amino group of a protein's N-terminal glycine residue. While a single human NMT cDNA has been isolated and characterized (hNMT-1), biochemical evidence has indicated the presence of several distinct NMTs in vivo, often varying in either apparent molecular weight and/or subcellular distribution. We now report the cloning and characterization of a second, genetically distinct human NMT (hNMT-2), as well as the isolation of the respective mouse NMT homologue for each human enzyme. The mouse and human versions of each NMT are highly homologous, displaying greater than 95% amino acid sequence identity. Comparisons between the NMT-1 and NMT-2 proteins revealed reduced levels of sequence identity (76-77%), indicating that NMT-1 and NMT-2 comprise two distinct families of N-myristoyltransferases. Transient transfection of either the hNMT-1 or hNMT-2 cDNA into COS-7 cells resulted in the expression of high levels of NMT enzyme activity. Both hNMT-1 and hNMT-2 were found to myristoylate several commonly studied peptide substrates with similar, hut distinguishable, relative selectivities. Western analysis revealed that while hNMT-2 appeared as a single 65-kDa protein in transfected COS-7 cells, hNMT-1 was processed to provide four distinct protein isoforms ranging from 49 to 68 kDa in size. Collectively, these studies demonstrate a heretofore unappreciated level of genetic complexity underlying the enzymology of N-terminal myristoylation and suggest that the specific inhibition or regulation of either NMT in vivo may in turn allow for the selective control of particular myristoylation-dependent cellular functions.