Designed beta-boomerang antiendotoxic and antimicrobial peptides: structures and activities in lipopolysaccharide.
Lipopolysaccharide (LPS), an integral part of the outer membrane of Gram-negative bacteria, is involved in a variety of biological processes including inflammation, septic shock, and resistance to host-defense molecules. LPS also provides an environment for folding of outer membrane proteins. In this work, we describe the structure-activity correlation of a series of 12-residue peptides in LPS. NMR structures of the peptides derived in complex with LPS reveal boomerang-like beta-strand conformations that are stabilized by intimate packing between the two aromatic residues located at the 4 and 9 positions. This structural feature renders these peptides with a high ability to neutralize endotoxicity, >80% at 10 nM concentration, of LPS. Replacements of these aromatic residues either with Ala or with Leu destabilizes the boomerang structure with the concomitant loss of antiendotoxic and antimicrobial activities. Furthermore, the aromatic packing stabilizing the beta-boomerang structure in LPS is found to be maintained even in a truncated octapeptide, defining a structured LPS binding motif. The mode of action of the active designed peptides correlates well with their ability to perturb LPS micelle structures. Fourier transform infrared spectroscopy studies of the peptides delineate beta-type conformations and immobilization of phosphate head groups of LPS. Trp fluorescence studies demonstrated selective interactions with LPS and the depth of insertion into the LPS bilayer. Our results demonstrate the requirement of LPS-specific structures of peptides for endotoxin neutralizations. In addition, we propose that structures of these peptides may be employed to design proteins for the outer membrane.
Bhunia
Anirban
A
School of Biological Sciences, Division of Structural and Computational Biology, Nanyang Technological University, Singapore 637551.
Mohanram
Harini
H
School of Biological Sciences, Division of Structural and Computational Biology, Nanyang Technological University, Singapore 637551.
Domadia
Prerna N
PN
School of Biological Sciences, Division of Structural and Computational Biology, Nanyang Technological University, Singapore 637551.
Torres
Jaume
J
School of Biological Sciences, Division of Structural and Computational Biology, Nanyang Technological University, Singapore 637551.
Bhattacharjya
Surajit
S
School of Biological Sciences, Division of Structural and Computational Biology, Nanyang Technological University, Singapore 637551.
D020816:Amino Acid Motifs; D000890:Anti-Infective Agents / Q000737:chemistry / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000494:pharmacology*; D002462:Cell Membrane / Q000378:metabolism; D004731:Endotoxins / Q000737:chemistry*; D006388:Hemagglutinins / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry; D008070:Lipopolysaccharides / Q000737:chemistry*; D008823:Micelles; D008826:Microbial Sensitivity Tests; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence / Q000379:methods; D013055:Spectrophotometry, Infrared / Q000379:methods
D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; D004731:Endotoxins; D006388:Hemagglutinins; D008051:Lipid Bilayers; D008070:Lipopolysaccharides; D008823:Micelles; D010455:Peptides