Mechanisms of RND multidrug efflux pumps.
Mechanisms of RND multidrug efflux pumps.
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DOI：
10.1016/j.bbapap.2008.10.004
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发表时间：
2009-05
期刊：
影响因子：
--
通讯作者：
Takatsuka Y
中科院分区：
文献类型：
--
作者：
Nikaido H;Takatsuka Y
RND（Resistance-Nodulation-Division）家族转运蛋白广泛存在于革兰氏阴性菌中，并催化许多抗生素和化疗药物的主动外排。它们具有非常大的周质结构域，并与外膜通道和周质衔接蛋白形成三重复合物。大肠杆菌的AcrAB-TolC复合物泵出非常广泛的药物，已经被最深入地研究。早期的研究表明，转运蛋白甚至可以捕获那些不能渗透穿过细胞质膜的底物，如双阴离子β-内酰胺，这表明捕获可以从周质发生。也有人建议，捕获发生从细胞质膜/周质界面，因为大多数基板含有一个相当大的疏水结构域，然而，这可能只是一个反映的性质的结合位点内AcrB。嵌合转运蛋白的遗传学研究表明，许多底物特异性是由其周质结构域决定的。最近，对完整细胞的生化研究导致了AcrB对某些β-内酰胺的动力学常数的测定，结果证实了AcrB是一个相当慢的泵的旧预测。重组纯化的AcrB及其亲属表明，泵是一种药物/质子逆向转运蛋白，AcrA强烈刺激泵的活性，并且AcrB似乎对共轭胆汁盐具有最高的亲和力。与跨膜结构域中的带电残基的网络的突变体的结构研究表明，质子化在这里产生了深远的构象变化，这被发现是存在于野生型AcrB的不对称晶体结构中的原聚体之一。功能旋转假说，然后预测，在周质域中的药物结合的挤出通过这种构象变化引发的质子化的残基之一，在上述网络，一个想法，最近支持的二硫键交联，以及由连接AcrB原聚体的行为。
RND (Resistance-Nodulation-Division) family transporters are widespread especially among Gram-negative bacteria, and catalyze the active efflux of many antibiotics and chemotherapeutic agents. They have very large periplasmic domains, and form tripartite complexes with outer membrane channels and periplasmic adaptor proteins. AcrAB-TolC complex of Escherichia coli, which pumps out a very wide range of drugs, has been studied most intensively. Early studies showed that the transporter captures even those substrates that cannot permeate across the cytoplasmic membrane, such as dianionic β-lactams, suggesting that the capture can occur from the periplasm. It was also suggested that the capture occurs from the cytoplasmic membrane/periplasm interface, because most substrates contain a sizable hydrophobic domain; however, this may simply be a reflection of the nature of the binding site within AcrB. Genetic studies of chimeric transporters showed that much of the substrate specificity is determined by their periplasmic domains. Biochemical studies with intact cells recently led to the determination of the kinetic constants of AcrB for some β-lactams, and the result confirms the old prediction that AcrB is a rather slow pump. Reconstitution of purified AcrB and its relatives showed that the pump is a drug/proton antiporter, that AcrA strongly stimulates the activity of the pump, and that AcrB seems to have a highest affinity for conjugated bile salts. Structural study with mutants of the network of charged residues in the transmembrane domain showed that protonation here produced a far-reaching conformational change, which was found to be present in one of the protomers in the asymmetric crystal structure of the wild-type AcrB. The functional rotatory hypothesis then predicts that the drug bound in the periplasmic domain is extruded through this conformational change initiated by the protonation of one of the residues in the aforementioned network, an idea that was recently supported by disulfide cross-linking as well as by the behavior of linked AcrB protomers.
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影响因子：
4.8
作者：
Eda, S;Maseda, H;Nakae, T
通讯作者：
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影响因子：
3.2
作者：
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通讯作者：
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影响因子：
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作者：
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DOI：
10.1073/pnas.0610160104
发表时间：
2007-03-13
影响因子：
11.1
作者：
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通讯作者：
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影响因子：
3.2
作者：
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通讯作者：
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