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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Trapping the transition state of an ATP-binding cassette transporter: Evidence for a concerted mechanism of maltose transport
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Trapping the transition state of an ATP-binding cassette transporter: Evidence for a concerted mechanism of maltose transport

机译：捕获ATP结合盒转运蛋白的过渡态：麦芽糖转运协调机制的证据

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摘要

High-affinity uptake into bacterial cells is mediated by a large class of periplasmic binding protein-dependent transport systems. members of the ATP-binding cassette superfamily. In the maltose transport system of Escherhoia coli the periplasmic maltose-bind- ing protein binds its substrate maltose with high affinity and. in addition, stimulates the ATPase activity of the membrane-associ- ated transporter when maltose is present. Vanadate inhibits mal- tose transport by trapping ADP in one of the two nucleotide- binding sites of the membrane transporter immediately after ATP' hydrolysis, consistent with its ability to mimic the transition state of the γ-phosphate of ATP during hydrolysis. Here we report that the maltose-binding protein becomes tightly associated with the membrane transporter in the presence of vanadate and simulta- neously loses its high affinity for maltose. These results suggest a general model explaining how ATP hydrolysis is coupled to sub- strate transport in which a binding protein stimulates the ATPase activity of its cognate transporter by stabilizing the transition state.
机译：一大类周质结合蛋白依赖性转运系统介导细菌细胞的高亲和力吸收。 ATP结合盒超家族的成员。在大肠杆菌的麦芽糖转运系统中，周质麦芽糖结合蛋白以高亲和力结合其底物麦芽糖。此外，当存在麦芽糖时，它会刺激膜相关转运蛋白的ATPase活性。钒酸盐通过在ATP'水解后立即将ADP捕获在膜转运蛋白的两个核苷酸结合位点之一中来抑制麦芽糖的运输，这与其在水解过程中模仿ATP的γ-磷酸盐过渡态的能力相符。在这里，我们报道在存在钒酸盐的情况下，麦芽糖结合蛋白与膜转运蛋白紧密结合，同时失去了对麦芽糖的高亲和力。这些结果提示了一个通用模型，该模型解释了ATP水解如何与底物运输耦合，其中结合蛋白通过稳定过渡态来刺激其同源运输蛋白的ATPase活性。

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