Two-dimensional 1H-NMR of transmembrane peptides from Escherichia coli phosphatidylglycerophosphate synthase in micelles

Sven Morein, Theodore P. Trouard, Jón B. Hauksson, Leif Rilfors, Gösta Arvidson, Göraji Lindblom

Research output: Contribution to journalArticle

19 Scopus citations

Abstract

Two 28-residue peptides, PTLLTLFRVILIPFFVLVFYKKKGKKKG [Pgs-(6-25)-peptidyl-KKKGKKKG; Pgs peptide A] and VEYAGIALFFVAAVLTLWSMLQYLSAAR [Pgs-(149-176)-peptide, Pgs peptide E], were synthesized and studied by CD and two-dimensional 1H-NMR spectroscopy. The first 20 amino acid residues of Pgs peptide A are identical to one predicted transmembrane segment (Pro6-Tyr25) of the integral membrane protein phosphatidylglycerophosphate synthase (Pgs) of Escherichia coli. Pgs peptide E is identical to another predicted transmembrane segment (Val149-Arg176), which is located in the C-terminal end of this lipid synthase. Pgs peptides A and E were dissolved in methanol or trifluoroethanol or were incorporated into solvent-free micelles of fully deuterated SDS. In all these systems, CD spectra of both peptides indicated an α-helical secondary structure. However, peptides that were solubilized in micelles exhibited the highest content of a-helix as judged from comparison of the CD spectra. Thermodynamically stable isotropic solutions at high peptide concentrations (1-3 mM) could only be obtained with the peptide incorporated in micelles; in organic solvents, significant peptide aggregation occurred. Relatively sharp peaks were obtained with 1H-NMR spectroscopy of the peptides in SDS micelles, which indicates rapid tumbling of the peptides in the micellar environment. Translational-diffusion coefficients of the micelles with and without peptide, determined by pulsed-field-gradient NMR, showed that the micellar size was unaffected by the solubilized peptide. The radius of the hydrated micelles was estimated to be about 2.7 nm (i.e. the mass of the aggregate is almost 30 kDa). Two-dimensional NMR spectroscopy of both peptides solubilized in the micelles indicated an a-helical conformation. This observation is strengthened by an investigation of the hydrogen exchange of the peptide amide protons, where significantly less exchange of the amide protons was observed in the middle of the peptides compared with the ends.

Original languageEnglish (US)
Pages (from-to)489-497
Number of pages9
JournalEuropean Journal of Biochemistry
Volume241
Issue number2
DOIs
StatePublished - Nov 5 1996
Externally publishedYes

Keywords

  • Circular dichroism
  • Hydrophobic peptide
  • NMR diffusion
  • Peptide conformation
  • Sodium dodecylsulfate micelle

ASJC Scopus subject areas

  • Biochemistry

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