Structural insights into the activation mechanism of melibiose permease by sodium binding
Structural insights into the activation mechanism of melibiose permease by sodium binding
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DOI：
10.1073/pnas.1008649107
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发表时间：
2010-12-21
影响因子：
11.1
通讯作者：
Lorenz-Fonfria, Victor A.
中科院分区：
文献类型：
--
作者：
Granell, Meritxell;Leon, Xavier;Lorenz-Fonfria, Victor A.
来自大肠杆菌（MelB）的蜜二糖载体将二糖蜜二糖的积累与H+、Na+或Li+的下坡进入偶联。在这项工作中，底物诱导的FTIR差光谱与荧光光谱相结合，定量比较MelB突变体的构象特性，牵连以前在钠结合，与那些全功能的半胱氨酸MelB通透酶。结果首次表明Asp 55和Asp 59是Na+结合的必需配体。其次，虽然Asp 124是不是必不可少的Na+结合，这个酸性残基可能发挥关键作用，可能是通过其与结合阳离子的相互作用，在充分的Na+诱导的构象变化所需的有效耦合之间的离子和糖结合位点;这个残基也可能是糖配体。第三，Asp 19不参与Na+结合，但它是蜜二糖配体。这些残基在两个独立的线程模型MelB的位置是一致的，他们提出的作用。
The melibiose carrier from Escherichia coli (MelB) couples the accumulation of the disaccharide melibiose to the downhill entry of H+, Na+, or Li+. In this work, substrate-induced FTIR difference spectroscopy was used in combination with fluorescence spectroscopy to quantitatively compare the conformational properties of MelB mutants, implicated previously in sodium binding, with those of a fully functional Cys-less MelB permease. The results first suggest that Asp55 and Asp59 are essential ligands for Na+ binding. Secondly, though Asp124 is not essential for Na+ binding, this acidic residue may play a critical role, possibly by its interaction with the bound cation, in the full Na+-induced conformational changes required for efficient coupling between the ion-and sugar-binding sites; this residue may also be a sugar ligand. Thirdly, Asp19 does not participate in Na+ binding but it is a melibiose ligand. The location of these residues in two independent threading models of MelB is consistent with their proposed role.