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NMR structure of pardaxin, a pore-forming antimicrobial peptide, in lipopolysaccharide micelles: mechanism of outer membrane permeabilization.

ABSTRACT: Lipopolysaccharide (LPS), the major constituent of the outer membrane of Gram-negative bacteria, is an important element against permeability of bactericidal agents, including antimicrobial peptides. However, structural determinants of antimicrobial peptides for LPS recognition are not clearly understood. Pardaxins (Pa1, Pa2, Pa3, and Pa4) are a group of pore-forming bactericidal peptides found in the mucous glands of sole fishes. Despite having a low net positive charge, pardaxins contain a broad spectrum of antibacterial activities. To elucidate the structural basis of LPS interactions of pardaxins, herein, we report the first three-dimensional structure of Pa4 bound to LPS micelles. The binding kinetics of Pa4 with LPS is estimated using [(15)N-Leu-19] relaxation dispersion NMR experiments. LPS/Pa4 interactions are further characterized by a number of biophysical methods, including isothermal titration calorimetry, (31)P NMR, saturation transfer difference NMR, dynamic light scattering, and IR spectroscopy. In the LPS-Pa4 complex, Pa4 adopts a unique helix-turn-helix conformation resembling a "horseshoe." Interestingly, the LPS-bound structure of Pa4 shows striking differences with the structures determined in lipid micelles or organic solvents. Saturation transfer difference NMR identifies residues of Pa4 that are intimately associated with LPS micelles. Collectively, our results provide mechanistic insights into the outer membrane permeabilization by pardaxin.

SUBMITTER: Bhunia A

PROVIDER: S-EPMC2823531 | biostudies-literature | 2010 Feb

REPOSITORIES: biostudies-literature

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NMR structure of pardaxin, a pore-forming antimicrobial peptide, in lipopolysaccharide micelles: mechanism of outer membrane permeabilization.

Bhunia Anirban A Domadia Prerna N PN Torres Jaume J Hallock Kevin J KJ Ramamoorthy Ayyalusamy A Bhattacharjya Surajit S

The Journal of biological chemistry 20091203 6

Lipopolysaccharide (LPS), the major constituent of the outer membrane of Gram-negative bacteria, is an important element against permeability of bactericidal agents, including antimicrobial peptides. However, structural determinants of antimicrobial peptides for LPS recognition are not clearly understood. Pardaxins (Pa1, Pa2, Pa3, and Pa4) are a group of pore-forming bactericidal peptides found in the mucous glands of sole fishes. Despite having a low net positive charge, pardaxins contain a bro ...[more]

PMID: 19959835

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Project description:BackgroundAntimicrobial peptides (AMPs) play important roles in the innate defense mechanism. The broad spectrum of activity of AMPs requires an efficient permeabilization of the bacterial outer and inner membranes. The outer leaflet of the outer membrane of Gram negative bacteria is made of a specialized lipid called lipopolysaccharide (LPS). The LPS layer is an efficient permeability barrier against anti-bacterial agents including AMPs. As a mode of protection, LPS can induce self associations of AMPs rendering them inactive. Temporins are a group of short-sized AMPs isolated from frog skin, and many of them are inactive against Gram negative bacteria as a result of their self-association in the LPS-outer membrane.Principal findingsUsing NMR spectroscopy, we have determined atomic resolution structure and characterized localization of temporin-1Ta or TA (FLPLIGRVLSGIL-amide) in LPS micelles. In LPS micelles, TA adopts helical conformation for residues L4-I12, while residues F1-L3 are found to be in extended conformations. The aromatic sidechain of residue F1 is involved in extensive packing interactions with the sidechains of residues P3, L4 and I5. Interestingly, a number of long-range NOE contacts have been detected between the N-terminal residues F1, P3 with the C-terminal residues S10, I12, L13 of TA in LPS micelles. Saturation transfer difference (STD) NMR studies demonstrate close proximity of residues including F1, L2, P3, R7, S10 and L13 with the LPS micelles. Notably, the LPS bound structure of TA shows differences with the structures of TA determined in DPC and SDS detergent micelles.SignificanceWe propose that TA, in LPS lipids, forms helical oligomeric structures employing N- and C-termini residues. Such oligomeric structures may not be translocated across the outer membrane; resulting in the inactivation of the AMP. Importantly, the results of our studies will be useful for the development of antimicrobial agents with a broader spectrum of activity.

Dataset Information

NMR structure of pardaxin, a pore-forming antimicrobial peptide, in lipopolysaccharide micelles: mechanism of outer membrane permeabilization.

Publications

NMR structure of pardaxin, a pore-forming antimicrobial peptide, in lipopolysaccharide micelles: mechanism of outer membrane permeabilization.

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