The University of Southampton
University of Southampton Institutional Repository

Interactions of anionic phospholipids and phosphatidylethanolamine with the potassium channel KcsA

Interactions of anionic phospholipids and phosphatidylethanolamine with the potassium channel KcsA
Interactions of anionic phospholipids and phosphatidylethanolamine with the potassium channel KcsA
Fluorescence quenching methods have been used to study interactions of anionic phospholipids with the potassium channel KcsA from Streptomyces lividans. Quenching of the Trp fluorescence of KcsA reconstituted into mixtures of dioleoylphosphatidylcholine (DOPC) and an anionic phospholipid with dibromostearoyl chains is more marked at low mole fractions of the brominated anionic phospholipid than is quenching in mixtures of dibromostearoylphosphatidylcholine and nonbrominated anionic lipid. The quenching data are consistent with two classes of binding site for lipid on KcsA, one set corresponding to annular binding sites around KcsA to which DOPC and two-chain anionic phospholipids bind with similar affinities, the other set (non-annular sites) corresponding to sites at which anionic phospholipids can bind but from which DOPC is either excluded or binds with very low affinity. The binding constant for tetraoleoylcardiolipin at the annular sites is significantly less than that for DOPC, being comparable to that for dioleoylphosphatidylethanolamine. Tetraoleoylcardiolipin binds with highest affinity to the non-annular sites, the affinity for dioleoylphosphatidylglycerol being the lowest. The affinity for dioleoylphosphatidylserine decreases at high ionic strength, suggesting that electrostatic interactions between the anionic phospholipid headgroup and positively charged residues on KcsA are important for binding at the non-annular site. The effect of ionic strength on the binding of phosphatidic acid is less marked than on phosphatidylserine. The value of the binding constant for the non-annular site depends on the extent of Trp fluorescence quenching following from binding at the non-annular site. It is suggested that the non-annular site to which binding is detected in the fluorescence quenching experiments corresponds to the binding site for phosphatidylglycerol detected at monomer-monomer interfaces in x-ray diffraction studies.

0006-3495
3828-3838
Alvis, Simon J.
c88b0bb5-db39-4559-a62c-ac5d772b5009
Williamson, Ian M.
73f00143-e678-4e05-8f99-1aa39f569aaf
East, J. Malcolm
9fe7f794-1d89-4935-9a99-b831d786056e
Lee, Anthong G.
0891914c-e0e2-4ee1-b43e-1b70eb072d8e
Alvis, Simon J.
c88b0bb5-db39-4559-a62c-ac5d772b5009
Williamson, Ian M.
73f00143-e678-4e05-8f99-1aa39f569aaf
East, J. Malcolm
9fe7f794-1d89-4935-9a99-b831d786056e
Lee, Anthong G.
0891914c-e0e2-4ee1-b43e-1b70eb072d8e

Alvis, Simon J., Williamson, Ian M., East, J. Malcolm and Lee, Anthong G. (2003) Interactions of anionic phospholipids and phosphatidylethanolamine with the potassium channel KcsA. Biophysical Journal, 85 (6), 3828-3838.

Record type: Article

Abstract

Fluorescence quenching methods have been used to study interactions of anionic phospholipids with the potassium channel KcsA from Streptomyces lividans. Quenching of the Trp fluorescence of KcsA reconstituted into mixtures of dioleoylphosphatidylcholine (DOPC) and an anionic phospholipid with dibromostearoyl chains is more marked at low mole fractions of the brominated anionic phospholipid than is quenching in mixtures of dibromostearoylphosphatidylcholine and nonbrominated anionic lipid. The quenching data are consistent with two classes of binding site for lipid on KcsA, one set corresponding to annular binding sites around KcsA to which DOPC and two-chain anionic phospholipids bind with similar affinities, the other set (non-annular sites) corresponding to sites at which anionic phospholipids can bind but from which DOPC is either excluded or binds with very low affinity. The binding constant for tetraoleoylcardiolipin at the annular sites is significantly less than that for DOPC, being comparable to that for dioleoylphosphatidylethanolamine. Tetraoleoylcardiolipin binds with highest affinity to the non-annular sites, the affinity for dioleoylphosphatidylglycerol being the lowest. The affinity for dioleoylphosphatidylserine decreases at high ionic strength, suggesting that electrostatic interactions between the anionic phospholipid headgroup and positively charged residues on KcsA are important for binding at the non-annular site. The effect of ionic strength on the binding of phosphatidic acid is less marked than on phosphatidylserine. The value of the binding constant for the non-annular site depends on the extent of Trp fluorescence quenching following from binding at the non-annular site. It is suggested that the non-annular site to which binding is detected in the fluorescence quenching experiments corresponds to the binding site for phosphatidylglycerol detected at monomer-monomer interfaces in x-ray diffraction studies.

Text
East_3.pdf - Version of Record
Restricted to Registered users only
Download (180kB)
Request a copy

More information

Published date: December 2003

Identifiers

Local EPrints ID: 24163
URI: https://eprints.soton.ac.uk/id/eprint/24163
ISSN: 0006-3495
PURE UUID: 39de3be0-5fd0-4b6b-9c2a-342d1b5f7bcd

Catalogue record

Date deposited: 24 Mar 2006
Last modified: 27 Feb 2019 17:31

Export record

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of https://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×