from the natural-selection dept.
According to a press release, researchers at the Rockefeller University Laboratory of Molecular Neurobiology and Biophysics have worked out the three-dimensional structure of the inner workings of an ion-channel protein complex. Ion channels act to pass only specific atoms through cell membranes, and thus act as biological ëatom sortersí. The channel examined in this study is specific for potassium ions.
The overall protein consists of four subunits, like four staves of a barrel. Inside the protein is a narrower tube called the selectivity filter where the potassium ion is recognized. The selectivity filter works as a sorter that chemically senses the ions as they go through the channel. When it senses another type of ion inside the channel, the filter prevents it from entering. The researchers discovered the structure of the filter is very finely tuned to pass potassium ions very quickly, but to exclude other kinds of atoms.
The work was reported in two papers in the 1 November 2001 issue of Nature. The Nature Science Update website has a brief summary of the research, with some helpful graphics.