Evidence for a trap-and-flip mechanism in a proton-dependent lipid transporter.
Evidence for a trap-and-flip mechanism in a proton-dependent lipid transporter.
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质子依赖性脂质转运体中捕获和翻转机制的证据。
DOI：
10.1038/s41467-022-28361-1
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发表时间：
2022-02-23
影响因子：
16.6
通讯作者：
Perez C
中科院分区：
文献类型：
--
作者：
Lambert E;Mehdipour AR;Schmidt A;Hummer G;Perez C
脂质跨膜转运是细胞中多种生物学途径的基础。多种离子偶联转运蛋白参与脂质转运，但其机制尚不清楚。主要易化因子超家族（MFS）脂质转运蛋白在细胞壁合成、脑发育和功能、脂质再循环和细胞信号传导中起着重要作用。最近的结构MFS脂质转运蛋白显示重叠的建筑特点指向一个共同的机制。在这里，我们使用半胱氨酸二硫键捕获、分子动力学模拟、突变分析以及体外和体内转运测定来研究LtaA的机制，LtaA是病原体金黄色葡萄球菌中脂磷壁酸合成所必需的质子依赖性MFS脂质转运蛋白。我们发现，LtaA显示不对称的横向开口与不同的功能相关性和循环通过外向和内向的构象是必不可少的运输活动。我们证明，虽然整个两亲性的LtaA中心腔有助于脂质结合，其亲水口袋决定底物特异性。我们建议，LtaA催化脂质转运的“陷阱和翻转”的机制，可能是共享MFS脂质转运。LtaA通过“捕获-翻转”机制催化糖脂转运，指出MFS脂质转运蛋白之间存在共享的机制模型。不对称的横向开口允许整个脂质基质进入两亲性中心腔。
Transport of lipids across membranes is fundamental for diverse biological pathways in cells. Multiple ion-coupled transporters take part in lipid translocation, but their mechanisms remain largely unknown. Major facilitator superfamily (MFS) lipid transporters play central roles in cell wall synthesis, brain development and function, lipids recycling, and cell signaling. Recent structures of MFS lipid transporters revealed overlapping architectural features pointing towards a common mechanism. Here we used cysteine disulfide trapping, molecular dynamics simulations, mutagenesis analysis, and transport assays in vitro and in vivo, to investigate the mechanism of LtaA, a proton-dependent MFS lipid transporter essential for lipoteichoic acid synthesis in the pathogen Staphylococcus aureus. We reveal that LtaA displays asymmetric lateral openings with distinct functional relevance and that cycling through outward- and inward-facing conformations is essential for transport activity. We demonstrate that while the entire amphipathic central cavity of LtaA contributes to lipid binding, its hydrophilic pocket dictates substrate specificity. We propose that LtaA catalyzes lipid translocation by a ‘trap-and-flip’ mechanism that might be shared among MFS lipid transporters. LtaA catalyzes glycolipid translocation by a ‘trap-and-flip’ mechanism, pointing to a shared mechanistic model among MFS lipid transporters. Asymmetric lateral openings allow access of the entire lipid substrate to the amphipathic central cavity.
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通讯作者：
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