Molecular mechanism underlying promiscuous polyamine recognition by spermidine acetyltransferase
Molecular mechanism underlying promiscuous polyamine recognition by spermidine acetyltransferase
复制标题
亚精胺乙酰转移酶混杂多胺识别的分子机制
DOI：
10.1016/j.biocel.2016.05.003
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
H. Matsumura
中科院分区：
文献类型：
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作者：
S. Sugiyama;S. Ishikawa;H. Tomitori;M. Niiyama;M. Hirose;Y. Miyazaki;K. Higashi;M. Murata;H. Adachi;K. Takano;S. Murakami;T. Inoue;Y. Mori;K. Kashiwagi;K. Igarashi;H. Matsumura
在原核细胞中，亚精胺乙酰转移酶(SAT)催化乙酰辅酶A向亚精胺转移，是控制多胺水平的关键酶。在这项研究中，我们测定了亚精胺(Spd)和辅酶A(CoA)在2.5°分辨率下的晶体结构。Sat是一个十二聚体，被组织为六个二聚体。SAT二聚体的二级结构元件和折叠拓扑结构类似于亚精胺/精胺N1-乙酰转移酶(SSAT)的二级结构元件和折叠拓扑结构，这表明SAT和SSAT之间存在进化联系。然而，SAT的多胺专一性与SSAT不同，是混杂的。SPD分子也位于二聚体间界面。Spd和CoA分子之间的距离为13°。一个深的、高度酸性的、充满水的空腔包围着Spd和CoA结合部位。基于结构的突变和体外试验确定了SPD结合的残基，以及腔壁上的酸性残基是酶活性所必需的。基于突变和结构数据，我们提出了一种支持多胺混杂识别SAT的乙酰化机制。
Spermidine acetyltransferase (SAT) fromEscherichia coli, which catalyses the transfer of acetyl groups from acetyl-CoA to spermidine, is a key enzyme in controlling polyamine levels in prokaryotic cells. In this study, we determined the crystal structure of SAT in complex with spermidine (SPD) and CoA at 2.5 Å resolution. SAT is a dodecamer organized as a hexamer of dimers. The secondary structural element and folding topology of the SAT dimer resemble those of spermidine/spermineN1-acetyltransferase (SSAT), suggesting an evolutionary link between SAT and SSAT. However, the polyamine specificity of SAT is distinct from that of SSAT and is promiscuous. The SPD molecule is also located at the inter-dimer interface. The distance between SPD and CoA molecules is 13 Å. A deep, highly acidic, water-filled cavity encompasses the SPD and CoA binding sites. Structure-based mutagenesis and in-vitro assays identified SPD-bound residues, and the acidic residues lining the walls of the cavity are mostly essential for enzymatic activities. Based on mutagenesis and structural data, we propose an acetylation mechanism underlying promiscuous polyamine recognition for SAT.