Role of side-edge site of sphingomyelinase from Bacillus cereus
Role of side-edge site of sphingomyelinase from Bacillus cereus
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DOI：
10.1016/j.bbrc.2012.04.120
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发表时间：
2012-05-25
影响因子：
3.1
通讯作者：
Sakurai, Jun
中科院分区：
文献类型：
--
作者：
Oda, Masataka;Takahashi, Masaya;Sakurai, Jun
蜡状芽孢杆菌鞘磷脂酶（Bacilluscereussphingomyelinase，Bc-SMase）属于镁离子依赖性中性鞘磷脂酶（neutralsphingomyelinase，nSMase），水解鞘磷脂（sphingomyelin，SM）产生磷酸胆碱和神经酰胺，是一种胞外溶血素。Bc-SMase具有两个金属离子结合位点，位于分子的长水平裂缝中，其中一个Mg 2+位于裂缝的中心区域，一个二价金属离子位于裂缝的侧边缘。Mg ~（2+）在Bc-SMase中长水平裂缝侧边的作用尚未得到解决。丙氨酸取代的Asn-57，Glu-99，和Asp-100位于靠近Mg 2+在侧边导致在绵羊红细胞或SM-脂质体的膜中的鞘磷脂的结合和水解的显着减少，但Phe-55没有。然而，这些残基的替换对酶活性几乎没有影响。N57 A、E99 A和D100 A含有2摩尔的Mg 2+。野生型和F55 A含有3 mol.晶体分析表明，具有Mg 2+的N57 A在侧边没有金属离子。这些结果表明，Bc-SMase侧边的Mg ~（2+）在其与细胞膜的结合中起重要作用。爱思唯尔公司出版
Bacillus cereus sphingomyelinase (Bc-SMase) belongs to the Mg2+-dependent neutral sphingomyelinase (nSMase) which hydrolyzes sphingomyelin (SM) to produce phosphocholine and ceramide, and acts as an extracellular hemolysin. Bc-SMase has two metal ion-binding sites in a long horizontal cleft across the molecule, with one Mg2+ in the central region of the cleft and one divalent metal ion at the side-edge of the cleft. The role of the Mg2+ at the side-edge of the long horizontal cleft in Bc-SMase remains unresolved. The replacement of Asn-57, Glu-99, and Asp-100 located in close proximity to Mg2+ at the side-edge with alanine resulted in a striking reduction in binding to and hydrolysis of sphingomyelin in membranes of sheep erythrocytes or SM-liposomes but that of Phe-55 did not. However, the replacement of these residues had little effect on the enzymatic activity. N57A, E99A, and D100A contained 2 mol of Mg2+. per mol of protein, and the wild type and F55A contained 3 mol. A crystal analysis showed that N57A with Mg2+ had no metal ion at the side-edge. These results indicate that the Mg2+ at the side-edge of Bc-SMase plays an important role in the binding to membranes. Published by Elsevier Inc.