Structural and Dynamic Insights into a Glycine-Mediated Short Analogue of a Designed Peptide in Lipopolysaccharide Micelles: Correlation Between Compact Structure and Anti-Endotoxin Activity

Biochemistry. 2017 Mar 7;56(9):1348-1362. doi: 10.1021/acs.biochem.6b01229. Epub 2017 Feb 21.

Abstract

In this study, we report an interaction study of a 13-residue analogue peptide VG13P (VARGWGRKCPLFG), derived from a designed VG16KRKP peptide (VARGWKRKCPLFGKGG), with a Lys6Gly mutation and removal of the last three residues Lys14-Gly15-Gly16, in lipopolysaccharide (LPS), a major component of the outer membrane of Gram-negative bacteria and responsible for sepsis or septic shock. VG13P displays an enhanced anti-endotoxin property as evident from significant reduction in LPS-induced TNF-α gene expression levels in a monocytic cell line, while it retains almost unchanged antimicrobial activity as its parent VG16KRKP against Gram-negative bacterial as well as fungal pathogens. In addition, in vitro LPS binding properties of VG13P in comparison to its parent VG16KRKP also remained unhindered, suggesting that the flexible C-terminal end of VG16KRKP may not play a major role in its observed antibacterial and LPS binding properties. An NMR-resolved solution structure of VG13P in LPS reveals two consecutive β-turns: one at the N-terminus, followed by another at the central region, closely resembling a rocking chair. The crucial Lys6Gly mutation along with C-terminal truncation from VG16KRKP reorients the hydrophobic hub in VG13P in a unique way so as to fold the N-terminal end back on itself, forming a turn and allowing Val1 and Ala2 to interact with Leu11 and Phe12 to bring the hydrophobic residues closer together to form a more compact hub compared to its parent. The hub is further strengthened via CH-π interaction between Gly4 and Phe12. This accounts for its improved anti-endotoxin activity as well as to its uninterrupted antimicrobial activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Bacteria / cytology
  • Bacteria / drug effects
  • Cell Line
  • Cell Membrane / drug effects
  • Drug Design*
  • Endotoxins / antagonists & inhibitors*
  • Glycine / metabolism*
  • Hemolysis / drug effects
  • Humans
  • Lipopolysaccharides / chemistry*
  • Micelles*
  • Models, Molecular
  • Peptides / chemistry*
  • Peptides / pharmacology*
  • Protein Conformation
  • Structure-Activity Relationship

Substances

  • Endotoxins
  • Lipopolysaccharides
  • Micelles
  • Peptides
  • Glycine