Analysis of crystalline and solution states of ligand-free spermidine N-acetyltransferase (SpeG) from Escherichia coli
Analysis of crystalline and solution states of ligand-free spermidine N-acetyltransferase (SpeG) from Escherichia coli
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DOI：
10.1107/s2059798319006545
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发表时间：
2019-06-01
影响因子：
2.2
通讯作者：
Anderson, Wayne F.
中科院分区：
文献类型：
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作者：
Filippova, Ekaterina V.;Weigand, Steven;Anderson, Wayne F.
亚精胺N-乙酰基转移酶(SpeG)将乙酰辅酶A上的乙酰基转移到胞内亚精胺的N端氨基上。这种乙酰化作用会使亚精胺失活，减少在某些化学和物理压力下往往会发生的多胺毒性。霍乱弧菌SpeG蛋白的结构特征是：虽然该单体具有与GCN5相关的N-乙酰转移酶超家族成员相似的结构折叠，但它的十二聚体结构仍然例外。本文对从大肠杆菌中分离到的SpeG进行了结构分析。像霍乱弧菌SpeG一样，大肠杆菌SpeG形成十二聚体，正如在1.75埃分辨率和2.9埃分辨率下测定的无配体的E.ColiSpeG十二聚体的两个晶体结构所揭示的那样。虽然霍乱弧菌SpeG和E.coliSpeG都可以采取不对称的开放十二聚体状态，但溶液分析表明，无配体的E.ColiSpeG的寡聚体组成与无配体的霍乱弧菌SpeG不同。基于这些数据，我们认为在没有配体的情况下，不同物种的SpeG寡聚体的平衡是不同的，因此对SpeG的功能可能是重要的。
Spermidine N-acetyltransferase (SpeG) transfers an acetyl group from acetyl-coenzyme A to an N-terminal amino group of intracellular spermidine. This acetylation inactivates spermidine, reducing the polyamine toxicity that tends to occur under certain chemical and physical stresses. The structure of the SpeG protein from Vibrio cholerae has been characterized: while the monomer possesses a structural fold similar to those of other Gcn5-related N-acetyltransferase superfamily members, its dodecameric structure remains exceptional. In this paper, structural analyses of SpeG isolated from Escherichia coli are described. Like V. cholerae SpeG, E.coli SpeG forms dodecamers, as revealed by two crystal structures of the ligand-free E. coli SpeG dodecamer determined at 1.75 and 2.9 angstrom resolution. Although both V. cholerae SpeG and E.coli SpeG can adopt an asymmetric open dodecameric state, solution analysis showed that the oligomeric composition of ligand-free E. coli SpeG differs from that of ligand-free V.cholerae SpeG. Based on these data, it is proposed that the equilibrium balance of SpeG oligomers in the absence of ligands differs from one species to another and thus might be important for SpeG function.