A light-driven sodium ion pump in marine bacteria

Nat Commun. 2013;4:1678. doi: 10.1038/ncomms2689.


Light-driven proton-pumping rhodopsins are widely distributed in many microorganisms. They convert sunlight energy into proton gradients that serve as energy source of the cell. Here we report a new functional class of a microbial rhodopsin, a light-driven sodium ion pump. We discover that the marine flavobacterium Krokinobacter eikastus possesses two rhodopsins, the first, KR1, being a prototypical proton pump, while the second, KR2, pumps sodium ions outward. Rhodopsin KR2 can also pump lithium ions, but converts to a proton pump when presented with potassium chloride or salts of larger cations. These data indicate that KR2 is a compatible sodium ion-proton pump, and spectroscopic analysis showed it binds sodium ions in its extracellular domain. These findings suggest that light-driven sodium pumps may be as important in situ as their proton-pumping counterparts.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Flavobacterium / metabolism*
  • Marine Biology*
  • Models, Molecular
  • Mutation
  • Sodium-Potassium-Exchanging ATPase / chemistry
  • Sodium-Potassium-Exchanging ATPase / genetics
  • Sodium-Potassium-Exchanging ATPase / metabolism*
  • Water Microbiology*


  • Sodium-Potassium-Exchanging ATPase