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Lipid interactions of acylated tryptophan‐methylated lactoferricin peptides by solid‐state NMR
Author(s) -
Greathouse Denise,
Vostrikov Vitaly,
McClellan Nicole,
Chipollini Juan,
Lay Jack,
Liyanage Rohana,
Ladd Taylor
Publication year - 2008
Publication title -
journal of peptide science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 66
eISSN - 1099-1387
pISSN - 1075-2617
DOI - 10.1002/psc.1047
Subject(s) - chemistry , peptide , antimicrobial peptides , lipid bilayer , residue (chemistry) , tryptophan , stereochemistry , nuclear magnetic resonance spectroscopy , solid state nuclear magnetic resonance , proton nmr , nmr spectra database , membrane , crystallography , biochemistry , amino acid , nuclear magnetic resonance , astronomy , spectral line , physics
Lactoferricin (LfB) is a 25‐residue innate immunity peptide released by pepsin from the N ‐terminal region of bovine lactoferrin. A smaller amidated peptide, LfB6 (RRWQWR‐NH 2 ) retains antimicrobial activity and is thought to constitute the “antimicrobial active‐site” (Tomita, Acta Paediatr Jpn. 1994; 36 : 585–91). Here we report on N ‐acylation of 1‐Me‐Trp 5 ‐LfB6, Cn‐RRWQ[1‐Me‐W]R‐NH 2 , where Cn is an acyl chain having n = 0, 2, 4, 6 or 12 carbons. Tryptophan 5 (Trp 5 ) was methylated to enhance membrane binding and to allow for selective deuteration at that position. Peptide/lipid interactions of Cn‐RRWQ[ 1‐Me‐W ]R‐NH 2 (deuterated 1‐Me‐Trp 5 underlined), were monitored by solid state 31 P NMR and 2 H NMR. The samples consisted of macroscopically oriented bilayers of mixed neutral (dimyristoylphosphatidylcholine, DMPC) and anionic (dimyristoylphosphatidylglycerol, DMPG) lipids in a 3:1 ratio with Cn‐RRWQ[& 1‐Me‐W ]R‐NH 2 peptides added at a 1:25 peptide to lipid ratio. 2 H‐NMR spectra reveal that the acylated peptides are well aligned in DMPC:DMPG bilayers. The 2 H NMR quadrupolar splittings suggest that the 1‐Me‐Trp is located in a motionally restricted environment, indicating partial alignment at the membrane interface. 31 P‐NMR spectra reveal that the lipids are predominantly in a bilayer configuration, with little perturbation by the peptides. Methylation alone, in C0‐RRWQ[1‐ Me‐W ]R‐NH 2 , resulted in a 3–4 fold increase in antimicrobial activity against E. coli . N ‐acylation with a C12 fatty acid enhanced activity almost 90 fold. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd.