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Biophys. J. BioFAST: First Published September 23, 2005. doi:10.1529/biophysj.105.063032
© 2005 by the Biophysical Society.

A more recent version of this article appeared on November 1, 2005.
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MEMBRANES

Properties and Structures of the Influenza and HIV Fusion Peptides on Lipid Membranes: Implications for a Role in Fusion

Md. Emdadul Haque 1, Vishwanath Koppaka 2, Paul H Axelsen 2 and Barry R Lentz 1*

1 UNC at Chapel Hill
2 University of Pennsylvania school of Medicine

* To whom correspondence should be addressed. E-mail: uncbrl{at}med.unc.edu.

Submitted on March 16, 2005
Revised on April 28, 2005
Accepted on 26 July 2005


  Abstract
The fusion peptides of HIV and influenza virus are crucial for viral entry into a host cell. In the present study, our goals were to determine (1) how fusion peptides modulate bilayer properties of fusogenic and nonfusogenic lipid vesicles and (2) whether fusion peptide structure is linked to bilayer structure or to the ability to promote fusion. Fluorescent probes revealed that neither peptide had a significant effect on bilayer packing at the interface. Both peptides increased acyl chain order in both fusogenic and non-fusogenic vesicles, but this effect was minimal below a peptide/lipid (P/L) ratio of 0.015 for gp41. Both peptides inhibited partitioning of a lipophilic fluorophore into membranes, although the gp41 fusion peptide had a smaller effect than HA peptide at low peptide concentrations, and its effect depended on membrane curvature. The influenza peptide was predominantly helical, and the gp41 peptide was predominantly antiparallel b-sheet when membrane bound, however the depths of penetration of both peptides into neutral membranes were similar and independent of membrane composition. Since both peptides promote the formation of fusion pores but not the formation of initial intermediates during PEG-mediated fusion, our results suggest that the effect of fusion peptides is mediated by their ability to occupy hydrophobic free volume rather than to their ability to adopt a particular secondary structure.

Key Words: anisotropy, bilayer properties, fusion peptides, membrane fusion, peptide structure, vesicles




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Copyright © 2005 by the Biophysical Society.