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Biophys. J. BioFAST: First Published October 7, 2005. doi:10.1529/biophysj.105.070466
© 2005 by the Biophysical Society.

A more recent version of this article appeared on January 1, 2006.
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MEMBRANES

TRANSMEMBRANE PEPTIDES STABILIZE INVERTED CUBIC PHASES IN A BIPHASIC LENGTH-DEPENDENT MANNER: IMPLICATIONS FOR PROTEIN-INDUCED MEMBRANE FUSION

David P. Siegel 1*, Vadim Cherezov 2, Denise V Greathouse 3, Roger E Koeppe II 3, Antoinette Killian 4 and Martin Caffrey 5

1 Givaudan, Inc.
2 The Ohio State University
3 University of Arkansas
4 University of Utrecht
5 The Ohio State Univeristy

* To whom correspondence should be addressed. E-mail: david.siegel{at}givaudan.com.

Submitted on July 11, 2005
Revised on August 11, 2005
Accepted on 13 September 2005


  Abstract
WALP peptides consist of repeating alanine-leucine sequences of different lengths, flanked with tryptophan "anchors" at each end. They form membrane-spanning {alpha}-helices in lipid membranes, and mimic protein transmembrane domains. WALP peptides of increasing length, from 19 to 31 amino acids, were incorporated into N-monomethylated dioleoylphosphatidylethanolamine (DOPE-Me) at concentrations up to 0.5 mole% peptide. When pure DOPE-Me is heated slowly, the lamellar (L{alpha}) phase first forms an inverted cubic (QII) phase, and the inverted hexagonal (HII) phase at higher temperatures. Using time-resolved x-ray diffraction and slow temperature scans (1.5 °C/h), WALP peptides were shown to decrease the temperatures of QII and HII phase formation (TQ and TH, respectively) as a function of peptide concentration. The shortest and longest peptides reduced TQ the most, while intermediate lengths had weaker effects. These findings are relevant to membrane fusion because the first step in the L{alpha}/QII phase transition is believed to be the formation of fusion pores between pure lipid membranes. These results imply that physiologically-relevant concentrations of these peptides could increase the susceptibility of biomembrane lipids to fusion through an effect on lipid phase behavior, and may explain one role of the membrane-spanning domains in the proteins that mediate membrane fusion.

Key Words: inverted phases, lipid phase behavior, lipid-peptide interactions, membrane-spanning domains, membrane-spanning peptides, nonlamellar phases




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D. P. Siegel
The Gaussian Curvature Elastic Energy of Intermediates in Membrane Fusion
Biophys. J., December 1, 2008; 95(11): 5200 - 5215.
[Abstract] [Full Text] [PDF]


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Copyright © 2005 by the Biophysical Society.