Crystal structure of Thermobifida fusca cis-prenyltransferase reveals the dynamic nature of its RXG motif-mediated inter-subunit interactions critical for its catalytic activity
Crystal structure of Thermobifida fusca cis-prenyltransferase reveals the dynamic nature of its RXG motif-mediated inter-subunit interactions critical for its catalytic activity
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DOI：
10.1016/j.bbrc.2020.08.062
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发表时间：
2020-11-12
影响因子：
3.1
通讯作者：
Koyama, Tanetoshi
中科院分区：
文献类型：
--
作者：
Kurokawa, Hirofumi;Ambo, Takanori;Koyama, Tanetoshi
顺式-戊烯基转移酶(cis-pt)催化异戊烯基二磷酸与烯丙基二磷酸受体的连续缩合反应，生成指定长度的线性聚戊烯基二磷酸。二聚体的形成是顺式催化所有顺戊烯基缩合反应的先决条件。在Cis中，一个保守的C-末端RXG基序形成亚基间相互作用并在催化活性中起作用，其结构与功能的关系引起了人们的广泛关注。在这里，我们解决了来自青海热双歧的中链顺式PT的晶体结构，它产生了十二碳二烯基二磷酸作为聚戊二烯类多糖的载体，用于细胞壁的合成。该结构揭示了一种特征的二聚体结构，其中一个单体的刚性RXG基序与另一单体的催化位形成亚基间氢键，而后者的RXG基序保持柔性。仔细的分析表明，两个单体亚基上的两个催化部位之间可能存在长期的负协同作用，允许一个亚基的结合稳定酶-底物三元复合体的形成，并促进镁-PPI的释放和随后在对应亚单位的分子内移位，从而使缩合反应可以在连续的循环中进行。目前的结构揭示了RXG基序的动态性质，并为进一步研究顺转录因子亚单位间的协同性提供了理论基础。(C)2020 Elsevier Inc.保留所有权利。
cis-Prenyltransferases (cis-PTs) catalyze consecutive condensations of isopentenyl diphosphate to an allylic diphosphate acceptor to produce a linear polyprenyl diphosphate of designated length. Dimer formation is a prerequisite for cis-PTs to catalyze all cis-prenyl condensation reactions. The structure-function relationship of a conserved C-terminal RXG motif in cis-PTs that forms inter-subunit interactions and has a role in catalytic activity has attracted much attention. Here, we solved the crystal structure of a medium-chain cis-PT from Thermobifida fusca that produces dodecaprenyl diphosphate as a polyprenoid glycan carrier for cell wall synthesis. The structure revealed a characteristic dimeric architecture of cis-PTs in which a rigidified RXG motif of one monomer formed inter-subunit hydrogen bonds with the catalytic site of the other monomer, while the RXG motif of the latter remained flexible. Careful analyses suggested the existence of a possible long-range negative cooperativity between the two catalytic sites on the two monomeric subunits that allowed the binding of one subunit to stabilize the formation of the enzyme-substrate ternary complex and facilitated the release of Mg-PPi and subsequent intra-molecular translocation at the counter subunit so that the condensation reaction could occur in consecutive cycles. The current structure reveals the dynamic nature of the RXG motif and provides a rationale for pursuing further investigations to elucidate the inter-subunit cooperativity of cis-PTs. (C) 2020 Elsevier Inc. All rights reserved.