Faculty Collaboration Database

Membrane binding, structure, and localization of cecropin-mellitin hybrid peptides: a site-directed spin-labeling study. Biophys J 2004 Jan;86(1 Pt 1):329-36

Date

12/26/2003

Pubmed ID

14695274

Pubmed Central ID

PMC1303797

DOI

10.1016/S0006-3495(04)74108-9

Scopus ID

2-s2.0-0347319182 (requires institutional sign-in at Scopus site)   60 Citations

Abstract

The interaction of antimicrobial peptides with membranes is a key factor in determining their biological activity. In this study we have synthesized a series of minimized cecropin-mellitin hybrid peptides each containing a single cysteine residue, modified the cysteine with the sulfhydryl-specific methanethiosulfonate spin-label, and used electron paramagnetic resonance spectroscopy to measure membrane-binding affinities and determine the orientation and localization of peptides bound to membranes that mimic the bacterial cytoplasmic membrane. All of the peptides were unstructured in aqueous solution but underwent a significant conformational change upon membrane binding that diminished the rotational mobility of the attached spin-label. Apparent partition coefficients were similar for five of the six constructs examined, indicating that location of the spin-label had little effect on peptide binding as long as the attachment site was in the relatively hydrophobic C-terminal domain. Depth measurements based on accessibility of the spin-labeled sites to oxygen and nickel ethylenediaminediacetate indicated that at high lipid/peptide ratios these peptides form a single alpha-helix, with the helical axis aligned parallel to the bilayer surface and immersed approximately 5 A below the membrane-aqueous interface. Such a localization would provide exposure of charged/polar residues on the hydrophilic face of the amphipathic helix to the aqueous phase, and allow the nonpolar residues along the opposite face of the helix to remain immersed in the hydrophobic phase of the bilayer. These results are discussed with respect to the mechanism of membrane disruption by antimicrobial peptides.

Author List

Bhargava K, Feix JB

Author

Jimmy B. Feix PhD Professor in the Biophysics department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Antimicrobial Cationic Peptides
Binding Sites
Electron Spin Resonance Spectroscopy
Insect Proteins
Liposomes
Melitten
Membrane Lipids
Membranes, Artificial
Protein Binding
Protein Conformation
Spin Labels