Crystal structures of substrate binding to Bacillus subtilis holo-(acyl carrier protein) synthase reveal a novel trimeric arrangement of molecules resulting in three active sites
Crystal structures of substrate binding to Bacillus subtilis holo-(acyl carrier protein) synthase reveal a novel trimeric arrangement of molecules resulting in three active sites
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DOI：
10.1016/s0969-2126(00)00178-7
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发表时间：
2000-08-15
期刊：
影响因子：
--
通讯作者：
Somers, WS
中科院分区：
文献类型：
--
作者：
Parris, KD;Lin, L;Somers, WS
背景：全酰基载体蛋白合酶（AcpS）是磷酸泛酰基转移酶超家族的成员，在脂肪酸生物合成途径中酰基载体蛋白（ACP）的功能激活中发挥着至关重要的作用。 AcpS 催化辅酶 A (CoA) 的 4'-磷酸泛酰胆碱基部分与 apo-ACP 上保守丝氨酸残基的侧链连接。结果：我们在此描述了来自枯草芽孢杆菌的 II 型 ACP 与其激活剂 AcpS 复合物的第一个晶体结构（2.3 埃）。我们还确定了单独的 AcpS（1.8 埃）和与 CoA 复合的 AcpS（1.5 埃）的结构。这些结构表明 AcpS 以三聚体形式存在，催化中心位于 AcpS 分子之间每个暴露于溶剂的交错处。定点诱变研究证实了三聚体形成在AcpS活性中的重要性。结论：AcpS中的活性位点仅在两个AcpS分子二聚化时形成。第三个分子的添加允许形成两个额外的活性位点，并且还允许每个AcpS分子的大疏水表面被埋在三聚体中。突变 Ile5-->Arg、Gln113-->Glu 和 Gln113-->Arg 表明 AcpS 在无法形成三聚体时处于失活状态。AcpS-CoA 和 AcpS-ACP 的共晶结构使我们能够提出此类 4'-磷酸泛酰胆碱基转移酶的催化机制。
Background: Holo-(acyl carrier protein) synthase (AcpS), a member of the phosphopantetheinyl transferase superfamily, plays a crucial role in the functional activation of acyl carrier protein (ACP) in the fatty acid biosynthesis pathway. AcpS catalyzes the attachment of the 4'-phosphopantetheinyl moiety of coenzyme A (CoA) to the sidechain of a conserved serine residue on apo-ACP.Results: We describe here the first crystal structure of a type II ACP from Bacillus subtilis in complex with its activator AcpS at 2.3 Angstrom. We also have determined the structures of AcpS alone (at 1.8 Angstrom) and AcpS in complex with CoA (at 1.5 Angstrom). These structures reveal that AcpS exists as a trimer, A catalytic center is located at each of the solvent-exposed interlaces between AcpS molecules. Site-directed mutagenesis studies confirm the importance of trimer formation in AcpS activity.Conclusions: The active site in AcpS is only formed when two AcpS molecules dimerize, The addition of a third molecule allows for the formation of two additional active sites and also permits a large hydrophobic surface from each molecule of AcpS to be buried in the trimer. The mutations Ile5-->Arg, Gln113-->Glu and Gln113-->Arg show that AcpS is inactive when unable to form a trimer, The co-crystal structures of AcpS-CoA and AcpS-ACP allow us to propose a catalytic mechanism for this class of 4'-phosphopantetheinyl transferases.