Crystal structure of a light-driven sodium pump

Recently, the first known light-driven sodium pumps, from the microbial rhodopsin family, were discovered. We have solved the structure of one of them, Krokinobacter eikastus rhodopsin 2 (KR2), in the monomeric blue state and in two pentameric red states, at resolutions of 1.45 A and 2.2 and 2.8 A, respectively. The structures reveal the ion-translocation pathway and show that the sodium ion is bound outside the protein at the oligomerization...