Datensatz

Zusammenfassung

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 Å and 2.2 and 2.8 Å, respectively. The structures reveal the ion-translocation pathway and show that the sodium ion is bound outside the protein at the oligomerization interface, that the ion-release cavity is capped by a unique N-terminal α-helix and that the ion-uptake cavity is unexpectedly large and open to the surface. Obstruction of the cavity with the mutation G263F imparts ​KR2 with the ability to pump potassium. These results pave the way for the understanding and rational design of cation pumps with new specific properties valuable for optogenetics.