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Penetration of lipid chains into transmembrane surfaces of membrane proteins: Studies with MscL

Penetration of lipid chains into transmembrane surfaces of membrane proteins: Studies with MscL
Penetration of lipid chains into transmembrane surfaces of membrane proteins: Studies with MscL
The transmembrane surface of a multi-helix membrane protein will be rough with cavities of various sizes between the transmembrane -helices. Efficient solvation of the surface by the lipid molecules that surround the protein in a membrane requires that the lipid fatty acyl chains be able to enter the cavities. This possibility has been investigated using fluorescence quenching methods. Trp residues have been introduced into lipid-facing sites in the first transmembrane -helix (M1) of the mechanosensitive channel of large-conductance MscL; lipid-facing residues at the N-terminal end of M1 are buried below the transmembrane surface of the protein. Fluorescence emission maxima for lipid-facing Trp residues in M1 vary with position in the bilayer comparably to those for Trp residues in the second transmembrane -helix (M2) despite the fact that lipid-facing residues in M2 are on the surface of the protein. Fluorescence emission spectra for most Trp residues on the periplasmic sides of M1 and M2 fit well to a model proposing a trough-like variation of dielectric constant across the membrane, but the relationship between location and fluorescence emission maximum on the cytoplasmic side of the membrane is more complex. The fluorescence of Trp residues in M1 is quenched efficiently by phospholipids with bromine-containing fatty acyl chains, showing that the lipid chains must be able to enter the Trp-containing cavities on the surface of MscL, resulting in efficient solvation of the surface.

0006-3495
3556-3563
Carney, J.
840c4dbe-b1a8-4cde-9281-dd8880e58078
East, J.M.
9fe7f794-1d89-4935-9a99-b831d786056e
Lee, A.G.
0891914c-e0e2-4ee1-b43e-1b70eb072d8e
Carney, J.
840c4dbe-b1a8-4cde-9281-dd8880e58078
East, J.M.
9fe7f794-1d89-4935-9a99-b831d786056e
Lee, A.G.
0891914c-e0e2-4ee1-b43e-1b70eb072d8e

Carney, J., East, J.M. and Lee, A.G. (2007) Penetration of lipid chains into transmembrane surfaces of membrane proteins: Studies with MscL. Biophysical Journal, 92, 3556-3563. (doi:10.1529/biophysj.106.102210).

Record type: Article

Abstract

The transmembrane surface of a multi-helix membrane protein will be rough with cavities of various sizes between the transmembrane -helices. Efficient solvation of the surface by the lipid molecules that surround the protein in a membrane requires that the lipid fatty acyl chains be able to enter the cavities. This possibility has been investigated using fluorescence quenching methods. Trp residues have been introduced into lipid-facing sites in the first transmembrane -helix (M1) of the mechanosensitive channel of large-conductance MscL; lipid-facing residues at the N-terminal end of M1 are buried below the transmembrane surface of the protein. Fluorescence emission maxima for lipid-facing Trp residues in M1 vary with position in the bilayer comparably to those for Trp residues in the second transmembrane -helix (M2) despite the fact that lipid-facing residues in M2 are on the surface of the protein. Fluorescence emission spectra for most Trp residues on the periplasmic sides of M1 and M2 fit well to a model proposing a trough-like variation of dielectric constant across the membrane, but the relationship between location and fluorescence emission maximum on the cytoplasmic side of the membrane is more complex. The fluorescence of Trp residues in M1 is quenched efficiently by phospholipids with bromine-containing fatty acyl chains, showing that the lipid chains must be able to enter the Trp-containing cavities on the surface of MscL, resulting in efficient solvation of the surface.

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More information

Published date: 1 May 2007

Identifiers

Local EPrints ID: 56404
URI: http://eprints.soton.ac.uk/id/eprint/56404
ISSN: 0006-3495
PURE UUID: c6e357cd-98bc-4138-b1d6-01903f09174d

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Date deposited: 07 Aug 2008
Last modified: 15 Mar 2024 11:01

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Contributors

Author: J. Carney
Author: J.M. East
Author: A.G. Lee

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