Structure of a Ternary Naa50p (NAT5/SAN) N-terminal Acetyltransferase Complex Reveals the Molecular Basis for Substrate-specific Acetylation
Structure of a Ternary Naa50p (NAT5/SAN) N-terminal Acetyltransferase Complex Reveals the Molecular Basis for Substrate-specific Acetylation
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DOI：
10.1074/jbc.m111.282863
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发表时间：
2011-10-21
影响因子：
4.8
通讯作者：
Marmorstein, Ronen
中科院分区：
文献类型：
--
作者：
Liszczak, Glen;Arnesen, Thomas;Marmorstein, Ronen
N-末端乙酰化的共翻译修饰在真核生物中普遍存在，并已被报道具有广泛的生物学效应。人N-末端乙酰转移酶（NAT）Naa 50 p（NAT 5/SAN）乙酰化含有N-末端甲硫氨酸残基的蛋白质的α-氨基，并且对于适当的姐妹染色单体凝聚和染色体凝聚是必需的。NAT的活性升高也与癌症相关，使这些酶成为有吸引力的治疗靶点。我们报告的X-射线晶体结构的Naa 50 p绑定到一个天然的底物肽片段和CoA。我们发现，底物的肽骨架通过一系列骨架氢键锚定到蛋白质上，第一个蛋氨酸残基通过多个货车德瓦尔斯接触指定，共同创建一个α-氨基蛋氨酸特异性口袋。我们还采用了基于结构的诱变;结果支持Naa 50 p的α-氨基甲硫氨酸特异性口袋的重要性，并且与保守的组氨酸和酪氨酸残基发挥重要催化作用的提议一致。与肽结合的Gcn 5组蛋白乙酰转移酶的三元Naa 50 p复合物的叠加显示，这两种酶共享Gcn 5相关的N-乙酰转移酶折叠，但在它们各自的底物结合凹槽中不同，使得Naa 50 p仅能容纳α-氨基底物，而不能容纳被赖氨酸乙酰转移酶如Gcn 5乙酰化的侧链赖氨酸底物。三元Naa 50 p复合物的结构还为设计具有可能的治疗应用的NAT特异性小分子抑制剂提供了第一个分子支架。
The co-translational modification of N-terminal acetylation is ubiquitous among eukaryotes and has been reported to have a wide range of biological effects. The human N-terminal acetyltransferase (NAT) Naa50p (NAT5/SAN) acetylates the alpha-amino group of proteins containing an N-terminal methionine residue and is essential for proper sister chromatid cohesion and chromosome condensation. The elevated activity of NATs has also been correlated with cancer, making these enzymes attractive therapeutic targets. We report the x-ray crystal structure of Naa50p bound to a native substrate peptide fragment and CoA. We found that the peptide backbone of the substrate is anchored to the protein through a series of backbone hydrogen bonds with the first methionine residue specified through multiple van der Waals contacts, together creating an alpha-amino methionine-specific pocket. We also employed structure-based mutagenesis; the results support the importance of the alpha-amino methionine-specific pocket of Naa50p and are consistent with the proposal that conserved histidine and tyrosine residues play important catalytic roles. Superposition of the ternary Naa50p complex with the peptide-bound Gcn5 histone acetyltransferase revealed that the two enzymes share a Gcn5-related N-acetyltransferase fold but differ in their respective substrate-binding grooves such that Naa50p can accommodate only an alpha-amino substrate and not a side chain lysine substrate that is acetylated by lysine acetyltransferase enzymes such as Gcn5. The structure of the ternary Naa50p complex also provides the first molecular scaffold for the design of NAT-specific small molecule inhibitors with possible therapeutic applications.