The light-driven sodium ion pump: A new player in rhodopsin research

Bioessays. 2016 Dec;38(12):1274-1282. doi: 10.1002/bies.201600065. Epub 2016 Nov 17.

Abstract

Rhodopsins are one of the most studied photoreceptor protein families, and ion-translocating rhodopsins, both pumps and channels, have recently attracted broad attention because of the development of optogenetics. Recently, a new functional class of ion-pumping rhodopsins, an outward Na+ pump, was discovered, and following structural and functional studies enable us to compare three functionally different ion-pumping rhodopsins: outward proton pump, inward Cl- pump, and outward Na+ pump. Here, we review the current knowledge on structure-function relationships in these three light-driven pumps, mainly focusing on Na+ pumps. A structural and functional comparison reveals both unique and conserved features of these ion pumps, and enhances our understanding about how the structurally similar microbial rhodopsins acquired such diverse functions. We also discuss some unresolved questions and future perspectives in research of ion-pumping rhodopsins, including optogenetics application and engineering of novel rhodopsins.

Keywords: KR2; crystal structure; light-driven ion pump; optogenetics; retinal; rhodopsin; structural biology.

Publication types

  • Review
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cation Transport Proteins / chemistry
  • Cation Transport Proteins / metabolism*
  • Humans
  • Light*
  • Models, Molecular
  • Optogenetics
  • Protein Conformation
  • Rhodopsin / chemistry
  • Rhodopsin / metabolism*
  • Sodium / metabolism*

Substances

  • Cation Transport Proteins
  • Rhodopsin
  • Sodium