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首页> 外文期刊>Journal of Molecular Biology >Structural Events in a Bacterial Uniporter Leading to Translocation of Glucose to the Cytosol
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Structural Events in a Bacterial Uniporter Leading to Translocation of Glucose to the Cytosol

机译：细菌单工商中的结构事件导致葡萄糖易位到胞浆溶胶

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Among classes of sugar transporters, there exists a comparatively new family of transporters named SWEET transporters (semi-SWEETS in bacteria) that are uniport transmembrane proteins. It is hypothesized that sugar is transported from the extracellular side (via outward-open state) to intracellular side (inward-open state) through intermediate occluded state (both extracellular and intracellular gates closed). In our study, extensive unbiased all-atom molecular dynamics simulations were carried out with the outward-open and inward-open conformations to study this transition mechanism. We find that after 100 ns, the outward-open structure without sugar bound starts changing to the occluded form leading to closure of extracellular gates stabilized by electrostatic and hydrophobic interactions. Further simulations (up to 7 mu s) have led to a transition toward the inward-open form and suggest that there exists more than one intermediate occluded conformation. We have also performed 5-mu s simulations on the glucose-docked structure to identify the putative substrate-bound translocation pathway. Glucose binds to semi-SWEET with strong hydrogen bonds to Asn66 and Trp50. Comparative simulations of substrate bound, and unbound forms suggested that glucose, the putative substrate, facilitates relatively rapid conformational transitions. For the first time, we captured the release of glucose to the cytosol, in this family of transporters. We find that prior to release of glucose, the glucose forms interactions with polar residues near the intracellular gate which may facilitate its release. The distance between the residues Asn31 and Gly34 of the other protomer was found to play a decisive role in the transport of glucose to the cytoplasmic side. (C) 2018 Elsevier Ltd. All rights reserved.
机译：在糖转运蛋白的类别中，存在具有甜型跨越式蛋白质的甜载体（细菌中半甜食）的相对新的运输司系列。假设通过中间闭塞状态（封闭细胞外和细胞内栅极）从细胞外侧（通过向外 - 开放状态）向细胞内侧（内向开放状态）向细胞内侧（内向开放状态）。在我们的研究中，通过向外开放和内向开放的构象进行广泛的无偏见的全原子分子动力学模拟，以研究这种过渡机制。我们发现，在100 ns之后，没有糖束的外开结构开始改变闭塞形式，导致通过静电和疏水相互作用稳定的细胞外门闭合。进一步的模拟（最多7μs）导致向内开放形式的过渡，并表明存在多于一个中间闭塞构象。我们还对葡萄糖对接结构进行了5-Mu S模拟，以识别推定的基板结合的易位途径。葡萄糖与半甜的结合，具有强氢键与ASN66和TRP50。基材绑定的比较模拟和未结合的形式建议葡萄糖，推定基板，促进相对快速的构象转变。我们第一次捕获葡萄糖到细胞溶胶，在这家运输王中。我们发现，在释放葡萄糖之前，葡萄糖形成与细胞内栅极附近的极性残基相互作用，这可以促进其释放。发现残留物ASN31和GLY34之间的距离在葡萄糖的转运中起着决定性作用在细胞质侧。 （c）2018年elestvier有限公司保留所有权利。

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