The authors determined the first high resolution structure of an ion channel, called KcsA from
the bacterium Streptomyces lividans. The structure that they revealed was perfectly adapted to allow entry of potassium ions while excluding smaller sodium ions, thus explaining the high K+ selectivity and the high transport rate for the first time.

In 2003 MacKinnon received half of the Nobel Prize in Chemistry for "for structural and mechanistic studies of ion channels."

Order of authorship in the original paper: Doyle, Cabral...MacKinnon.

(Thanks to Juan Weiss for this reference and its interpretation.)