Development of potent anti-infective agents from Silurana tropicalis: Conformational analysis of the amphipathic, alpha-helical antimicrobial peptide XT-7 and its non-haemolytic analogue [G4K]XT-7

Anusha P. Subasinghage, J. Michael Conlon, Chandralal M. Hewage

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)

Abstract

Peptide XT-7 (GLLGP5LLKIA10AKVGS15NLL.NH2 ) is a cationic, leucine-rich peptide, first isolated from skin secretions of the frog, Silurana tropicalis (Pipidae). The peptide shows potent, broad-spectrum antimicrobial activity but its therapeutic potential is limited by haemolytic activity (LC50 = 140 μM). The analogue [G4K]XT-7, however, retains potent antimicrobial activity but is non-haemolytic (LC50 > 500 μM). In order to elucidate the molecular basis for this difference in properties, the three dimensional structures of XT-7 and the analogue have been investigated by proton NMR spectroscopy and molecular modelling. In aqueous solution, both peptides lack secondary structure. In a 2,2,2-trifluoroethanol (TFE-d3)-H2O mixed solvent system, XT-7 is characterised by a right handed α-helical conformation between residues Leu3 and Leu17 whereas [G4K]XT-7 adopts a more restricted α-helical conformation between residues Leu6 and Leu17. A similar conformation for XT-7 in 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) micellular media was observed with a helical segment between Leu3 and Leu17. However, differences in side chain orientations restricting the hydrophilic residues to a smaller patch resulted in an increased hydrophobic surface relative to the conformation in TFE-H2O. Molecular modelling of the structures obtained in our study demonstrates the amphipathic character of the helical segments. It is proposed that the marked decrease in haemolytic activity produced by the substitution Gly4 → Lys in XT-7 arises from a decrease in both helicity and hydrophobicity. These studies may facilitate the development of potent but non-toxic anti-infective agents based upon the structure of XT-7.

Original languageEnglish
Pages (from-to)1020-1028
Number of pages9
JournalBiochimica et Biophysica Acta - Proteins and Proteomics
Volume1804
Issue number4
DOIs
Publication statusPublished - Apr 2010
Externally publishedYes

Keywords

  • Amphipathic α-helix
  • Antimicrobial
  • NMR
  • Silurana tropicalis
  • XT-7

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biophysics
  • Biochemistry
  • Molecular Biology

Fingerprint

Dive into the research topics of 'Development of potent anti-infective agents from Silurana tropicalis: Conformational analysis of the amphipathic, alpha-helical antimicrobial peptide XT-7 and its non-haemolytic analogue [G4K]XT-7'. Together they form a unique fingerprint.

Cite this