Functional evidence for a supramolecular structure for the Streptomyces lividans potassium channel KcsA

Biochem Biophys Res Commun. 2004 Sep 24;322(3):1059-65. doi: 10.1016/j.bbrc.2004.08.027.

Abstract

Here we present functional evidence for involvement of poly-(R)-3-hydroxybutyrate (PHB) and inorganic polyphosphate (polyP) in ion conduction and selection at the intracellular side of the Streptomyces lividans potassium channel, KcsA. At < or = 25 degrees C, KcsA forms channels in planar bilayers that display signal characteristics of PHB/polyP channels at the intracellular side; i.e., a preference for divalent Mg(2+) cations at pH 7.2, and a preference for monovalent K+ cations at pH 6.8. Between 25 and 26 degrees C, KcsA undergoes a transition to a new conformation in which the channel exhibits high selectivity for K+, regardless of solution pH. This suggests that basic residues of the C-terminal polypeptides have moved closer to the polyP end unit, reducing its negative charge. The data support a supramolecular structure for KcsA in which influx of ions is prevented by the selectivity pore, whereas efflux of K+ is governed by a conductive core of PHB/polyP in partnership with the C-terminal polypeptide strands.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacterial Proteins / drug effects
  • Bacterial Proteins / isolation & purification
  • Bacterial Proteins / physiology*
  • Cations, Divalent / pharmacology
  • Chlorides / pharmacology
  • Hydrogen-Ion Concentration
  • Lipid Bilayers
  • Magnesium / pharmacology
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Patch-Clamp Techniques
  • Potassium Channels / drug effects
  • Potassium Channels / isolation & purification
  • Potassium Channels / physiology*
  • Streptomyces / physiology*
  • Thermodynamics

Substances

  • Bacterial Proteins
  • Cations, Divalent
  • Chlorides
  • Lipid Bilayers
  • Potassium Channels
  • prokaryotic potassium channel
  • Magnesium