PerspectiveStructural Biology

(Pseudo-)Symmetrical Transport

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Science  25 Jan 2013:
Vol. 339, Issue 6118, pp. 399-401
DOI: 10.1126/science.1228465

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Summary

Most walls incorporate some way of getting through them, such as a gate, a revolving door, or an airlock. The airlock concept is also used in moving cargo across cell membranes, for example, for intake of nutrients or expulsion of toxins, which is often an uphill battle against a concentration gradient. Nature fights this battle using membrane-embedded proteins called transporters. These proteins can alternate between at least two preferred conformations. In one of those conformations, the cargo diffuses in and binds to its binding site. The first door then shuts and the other opens, providing unhindered access to the other side of the membrane. Recent studies suggest a key role for structural symmetry in this process.