Crystal Structure of a Potassium Ion Transporter, TrkH

Nature. 2011 Mar 17;471(7338):336-40. doi: 10.1038/nature09731. Epub 2011 Feb 13.

Abstract

The TrkH/TrkG/KtrB proteins mediate K(+) uptake in bacteria and probably evolved from simple K(+) channels by multiple gene duplications or fusions. Here we present the crystal structure of a TrkH from Vibrio parahaemolyticus. TrkH is a homodimer, and each protomer contains an ion permeation pathway. A selectivity filter, similar in architecture to those of K(+) channels but significantly shorter, is lined by backbone and side-chain oxygen atoms. Functional studies showed that TrkH is selective for permeation of K(+) and Rb(+) over smaller ions such as Na(+) or Li(+). Immediately intracellular to the selectivity filter are an intramembrane loop and an arginine residue, both highly conserved, which constrict the permeation pathway. Substituting the arginine with an alanine significantly increases the rate of K(+) flux. These results reveal the molecular basis of K(+) selectivity and suggest a novel gating mechanism for this large and important family of membrane transport proteins.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP-Binding Cassette Transporters / chemistry
  • Amino Acid Sequence
  • Crystallography, X-Ray
  • Escherichia coli Proteins / chemistry
  • Ion Channel Gating
  • Ion Transport
  • Models, Molecular
  • Molecular Sequence Data
  • Potassium / metabolism
  • Potassium Channels / chemistry*
  • Potassium Channels / metabolism*
  • Structure-Activity Relationship
  • Substrate Specificity
  • Vibrio parahaemolyticus / chemistry*

Substances

  • ATP-Binding Cassette Transporters
  • Escherichia coli Proteins
  • Potassium Channels
  • TrkH protein, E coli
  • Potassium

Associated data

  • PDB/3PJZ