Journal:Acta Cryst D:S205979832001517X
From Proteopedia
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Apical sodium-dependent bile acid transporter (ASBT) is a membrane transporter protein which recycles bile acids from small intestine into enterocytes. It is a potential drug target for treating several metabolic diseases including type 2 diabetes. To date, high-resolution structures are only available for two bacterial ASBT proteins, which provide structural information to help understand how a bile acid is transported by ASBT. To do so, a minimum of two ASBT conformational states have to be obtained, one facing outside of the cell and the other facing inside. However, currently the only outward-facing ASBT structure is obtained with a severely crippled ASBT protein, whose normal functions such as binding and transport of bile acids are nearly lost. Therefore, the outward-facing state of ASBT needs validation. | Apical sodium-dependent bile acid transporter (ASBT) is a membrane transporter protein which recycles bile acids from small intestine into enterocytes. It is a potential drug target for treating several metabolic diseases including type 2 diabetes. To date, high-resolution structures are only available for two bacterial ASBT proteins, which provide structural information to help understand how a bile acid is transported by ASBT. To do so, a minimum of two ASBT conformational states have to be obtained, one facing outside of the cell and the other facing inside. However, currently the only outward-facing ASBT structure is obtained with a severely crippled ASBT protein, whose normal functions such as binding and transport of bile acids are nearly lost. Therefore, the outward-facing state of ASBT needs validation. | ||
| - | In this study, a bacterial ASBT, called | + | In this study, a bacterial ASBT, called ASBT<sub>Yf</sub>, is engineered to have its intracellular parts connected by a disulfide bond, so that it will be trapped in an outward-facing state. Before this engineered ASBT<sub>Yf</sub> is trapped, it folds and moves like the wild-type protein. More importantly, it remains functional since it binds bile acids as normal. Then after the conformational trap, this ASBT<sub>Yf</sub> is found to open outwardly in its structure. In other words, a wild-type-like ASBT protein is trapped in a state facing outside of the cell, demonstrating that this outward-facing state is of physiological relevance. Meanwhile, a low-affinity ligand-like molecule, citrate, binds to the substrate-binding site in the trapped outward-facing ASBT structure, further indicating that the trapped ASBT protein retains its functionality. These data validate a physiological outward-facing state in ASBT, and advance out understanding toward its transport mechanism. |
<b>References</b><br> | <b>References</b><br> | ||
Revision as of 11:01, 13 December 2020
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