Structure of dimeric SecA, the Escherichia coli preprotein translocase motor
Structure of dimeric SecA, the Escherichia coli preprotein translocase motor
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DOI：
10.1016/j.jmb.2006.12.049
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发表时间：
2007-03-09
影响因子：
5.6
通讯作者：
Petratos, Kyriacos
中科院分区：
文献类型：
--
作者：
Papanikolau, Yannis;Papadovasilaki, Maria;Petratos, Kyriacos
SecA 是前蛋白转位酶 ATP 酶亚基和超家族 2 (SF2) RNA 解旋酶。在这里，我们展示了 apo 形式的大肠杆菌 SecA 同二聚体的 2 埃晶体结构，以及与 ATP、ADP 和腺苷 5-β-γ-亚氨基三磷酸 (AMP-PNP) 的复合物。每个单体包含由两个结构域（核苷酸结合结构域，NBD 和 ATPase 2 分子内调节器，IRA2）组成的 SF2 ATPase 核心（DEAD 电机）、插入 NBD 的前蛋白结合结构域 (PBD) 和与 IRA2 连接的羧基末端结构域（C 结构域）。 SecA 的核苷酸复合物的结构识别出位于两个 DEAD 运动结构域和对 ATP 催化至关重要的残基之间的界面核苷酸结合裂缝。该二聚体包含两个几乎相同的原聚体，以反平行方式缔合。二聚化仅通过 DEAD 运动结构域的广泛接触来介导，使 C 结构域从二聚化核心面向外。这种二聚化模式解释了功能上重要的突变的影响，并且与为其他 SecA 结构提出的二聚化模型完全不同。讨论了这些发现对易位酶组装和催化的影响。 (c) 2006 Elsevier Ltd. 保留所有权利。
SecA is the preprotein translocase ATPase subunit and a superfamily 2 (SF2) RNA helicase. Here we present the 2 angstrom crystal structures of the Escherichia coli SecA homodimer in the apo form and in complex with ATP, ADP and adenosine 5-[beta-gamma-imido]triphosphate (AMP-PNP). Each monomer contains the SF2 ATPase core (DEAD motor) built of two domains (nucleotide binding domain, NBD and intramolecular regulator of ATPase 2, IRA2), the preprotein binding domain (PBD), which is inserted in NBD and a carboxy-terminal domain (C-domain) linked to IRA2. The structures of the nucleotide complexes of SecA identify an interfacial nucleotide-binding cleft located between the two DEAD motor domains and residues critical for ATP catalysis. The dimer comprises two virtually identical protomers associating in an antiparallel fashion. Dirnerization is mediated solely through extensive contacts of the DEAD motor domains leaving the C-domain facing outwards from the dimerization core. This dimerization mode explains the effect of functionally important mutations and is completely different from the dimerization models proposed for other SecA structures. The repercussion of these findings on translocase assembly and catalysis is discussed. (c) 2006 Elsevier Ltd. All rights reserved.