Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain
the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in
Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles
and JavaScript.
An X-ray crystal structure of an organic anion transporter identifies it as an ion channel instead. Its similarity to an unrelated family of water channels raises evolutionary questions that have been recently bubbling up around membrane proteins.