Gramicidin structure and disposition in highly curved membranes

Wei Liu, M. Caffrey

Research output: Contribution to journalArticle

40 Citations (Scopus)

Abstract

With a view to deciphering aspects of the mechanism of membrane protein crystallization in lipidic mesophases (in meso crystallization), an examination of the structure and disposition of the pore-forming peptide, gramicidin, in the lipidic cubic phase was undertaken. At its simplest, the cubic phase consists of lipid and water in the form of a molecular 'sponge.' The lipid exists as a continuous, highly curved bilayer that divides the aqueous component into two interpenetrating but non-contacting channels. In this study, we show that gramicidin reconstitutes into the lipid bilayer of the cubic phase and that it adopts the channel, or helical dimer, conformation therein. Fluorescence quenching with brominated lipid was used to establish the bilayer location of the peptide. Electronic absorption and emission spectroscopies corroborated this finding. Peptide conformation in the cubic phase membrane was determined by circular dichroism. The identity and microstructure of the mesophases, and their capacity to accommodate gramicidin and other system components (sodium dodecyl sulfate, trifluoroethanol), was established by small-angle X-ray diffraction. Beyond a limiting concentration, gramicidin destabilized the cubic phase in favor of the inverted hexagonal phase. While gramicidin remained bilayer bound as membrane thickness changed, its conformation responded to the degree of bilayer mismatch with the hydrophobic surface of the peptide. These findings support the hypothesis that reconstitution into the lipid bilayer is an integral part of the in meso crystallization process as applied to membrane proteins. They also suggest ways for improving the process of membrane protein crystallogenesis.

Original languageEnglish (US)
Pages (from-to)23-40
Number of pages18
JournalJournal of Structural Biology
Volume150
Issue number1
DOIs
StatePublished - Apr 2005
Externally publishedYes

Fingerprint

Gramicidin
Crystallization
Membranes
Peptides
Membrane Proteins
Lipid Bilayers
Lipids
Trifluoroethanol
Porifera
Circular Dichroism
X-Ray Diffraction
Sodium Dodecyl Sulfate
Spectrum Analysis
Fluorescence
Water

Keywords

  • Bilayer thickness mismatch
  • Circular dichroism
  • Crystallization
  • Cubic phase
  • Fluorescence quenching
  • X-ray diffraction

ASJC Scopus subject areas

  • Structural Biology

Cite this

Gramicidin structure and disposition in highly curved membranes. / Liu, Wei; Caffrey, M.

In: Journal of Structural Biology, Vol. 150, No. 1, 04.2005, p. 23-40.

Research output: Contribution to journalArticle

@article{161da9942764463fae680471b7508304,
title = "Gramicidin structure and disposition in highly curved membranes",
abstract = "With a view to deciphering aspects of the mechanism of membrane protein crystallization in lipidic mesophases (in meso crystallization), an examination of the structure and disposition of the pore-forming peptide, gramicidin, in the lipidic cubic phase was undertaken. At its simplest, the cubic phase consists of lipid and water in the form of a molecular 'sponge.' The lipid exists as a continuous, highly curved bilayer that divides the aqueous component into two interpenetrating but non-contacting channels. In this study, we show that gramicidin reconstitutes into the lipid bilayer of the cubic phase and that it adopts the channel, or helical dimer, conformation therein. Fluorescence quenching with brominated lipid was used to establish the bilayer location of the peptide. Electronic absorption and emission spectroscopies corroborated this finding. Peptide conformation in the cubic phase membrane was determined by circular dichroism. The identity and microstructure of the mesophases, and their capacity to accommodate gramicidin and other system components (sodium dodecyl sulfate, trifluoroethanol), was established by small-angle X-ray diffraction. Beyond a limiting concentration, gramicidin destabilized the cubic phase in favor of the inverted hexagonal phase. While gramicidin remained bilayer bound as membrane thickness changed, its conformation responded to the degree of bilayer mismatch with the hydrophobic surface of the peptide. These findings support the hypothesis that reconstitution into the lipid bilayer is an integral part of the in meso crystallization process as applied to membrane proteins. They also suggest ways for improving the process of membrane protein crystallogenesis.",
keywords = "Bilayer thickness mismatch, Circular dichroism, Crystallization, Cubic phase, Fluorescence quenching, X-ray diffraction",
author = "Wei Liu and M. Caffrey",
year = "2005",
month = "4",
doi = "10.1016/j.jsb.2004.12.007",
language = "English (US)",
volume = "150",
pages = "23--40",
journal = "Journal of Structural Biology",
issn = "1047-8477",
publisher = "Academic Press Inc.",
number = "1",

}

TY - JOUR

T1 - Gramicidin structure and disposition in highly curved membranes

AU - Liu, Wei

AU - Caffrey, M.

PY - 2005/4

Y1 - 2005/4

N2 - With a view to deciphering aspects of the mechanism of membrane protein crystallization in lipidic mesophases (in meso crystallization), an examination of the structure and disposition of the pore-forming peptide, gramicidin, in the lipidic cubic phase was undertaken. At its simplest, the cubic phase consists of lipid and water in the form of a molecular 'sponge.' The lipid exists as a continuous, highly curved bilayer that divides the aqueous component into two interpenetrating but non-contacting channels. In this study, we show that gramicidin reconstitutes into the lipid bilayer of the cubic phase and that it adopts the channel, or helical dimer, conformation therein. Fluorescence quenching with brominated lipid was used to establish the bilayer location of the peptide. Electronic absorption and emission spectroscopies corroborated this finding. Peptide conformation in the cubic phase membrane was determined by circular dichroism. The identity and microstructure of the mesophases, and their capacity to accommodate gramicidin and other system components (sodium dodecyl sulfate, trifluoroethanol), was established by small-angle X-ray diffraction. Beyond a limiting concentration, gramicidin destabilized the cubic phase in favor of the inverted hexagonal phase. While gramicidin remained bilayer bound as membrane thickness changed, its conformation responded to the degree of bilayer mismatch with the hydrophobic surface of the peptide. These findings support the hypothesis that reconstitution into the lipid bilayer is an integral part of the in meso crystallization process as applied to membrane proteins. They also suggest ways for improving the process of membrane protein crystallogenesis.

AB - With a view to deciphering aspects of the mechanism of membrane protein crystallization in lipidic mesophases (in meso crystallization), an examination of the structure and disposition of the pore-forming peptide, gramicidin, in the lipidic cubic phase was undertaken. At its simplest, the cubic phase consists of lipid and water in the form of a molecular 'sponge.' The lipid exists as a continuous, highly curved bilayer that divides the aqueous component into two interpenetrating but non-contacting channels. In this study, we show that gramicidin reconstitutes into the lipid bilayer of the cubic phase and that it adopts the channel, or helical dimer, conformation therein. Fluorescence quenching with brominated lipid was used to establish the bilayer location of the peptide. Electronic absorption and emission spectroscopies corroborated this finding. Peptide conformation in the cubic phase membrane was determined by circular dichroism. The identity and microstructure of the mesophases, and their capacity to accommodate gramicidin and other system components (sodium dodecyl sulfate, trifluoroethanol), was established by small-angle X-ray diffraction. Beyond a limiting concentration, gramicidin destabilized the cubic phase in favor of the inverted hexagonal phase. While gramicidin remained bilayer bound as membrane thickness changed, its conformation responded to the degree of bilayer mismatch with the hydrophobic surface of the peptide. These findings support the hypothesis that reconstitution into the lipid bilayer is an integral part of the in meso crystallization process as applied to membrane proteins. They also suggest ways for improving the process of membrane protein crystallogenesis.

KW - Bilayer thickness mismatch

KW - Circular dichroism

KW - Crystallization

KW - Cubic phase

KW - Fluorescence quenching

KW - X-ray diffraction

UR - http://www.scopus.com/inward/record.url?scp=15444380710&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=15444380710&partnerID=8YFLogxK

U2 - 10.1016/j.jsb.2004.12.007

DO - 10.1016/j.jsb.2004.12.007

M3 - Article

VL - 150

SP - 23

EP - 40

JO - Journal of Structural Biology

JF - Journal of Structural Biology

SN - 1047-8477

IS - 1

ER -