2b5k
From Proteopedia
|
PV5 NMR solution structure in DPC micelles
Overview
The horseshoe crab cationic antimicrobial peptide polyphemusin I is highly, active in vitro but not protective in mouse models of bacterial and LPS, challenge, while a synthetic polyphemusin variant, PV5, was previously, shown to be protective in vivo. In this study, we investigated the, interaction of these peptides with lipid membranes in an effort to propose, a mechanism of interaction. The solution structure of PV5 was determined, by proton NMR in the absence and presence of dodecylphosphocholine (DPC), micelles. Like polyphemusin I, PV5 is a beta-hairpin but appeared less, amphipathic in solution. Upon association with DPC micelles, PV5 underwent, side chain rearrangements which resulted in an increased amphipathic, conformation. Using fluorescence spectroscopy, both peptides were found to, have limited affinity for neutral vesicles composed of phosphatidylcholine, (PC). Incorporation of 25 mol % cholesterol or phosphatidylethanolamine, into PC vesicles produced little change in the partitioning of either, peptide. Incorporation of 25 mol % phosphatidylglycerol (PG) into PC, vesicles, a simple prokaryotic model, resulted in a large increase in the, affinity for both peptides, but the partition coefficient for PV5 was, almost twice that of polyphemusin I. Differential scanning calorimetry, studies supported the partitioning data and demonstrated that neither, peptide interacted readily with neutral PC vesicles. Both peptides showed, affinity for negatively charged membranes incorporating PG. The affinity, of PV5 was much greater as the pretransition peak was absent at low, peptide to lipid ratios (1:400) and the reduction in enthalpy of the main, transition was greater than that produced by polyphemusin I. Both peptides, decreased the lamellar to inverted hexagonal phase transition temperature, of PE indicating the induction of negative curvature strain. These, results, combined with previous findings that polyphemusin I promotes, lipid flip-flop but does not induce significant vesicle leakage, ruled out, the torroidal pore and carpet mechanisms of antimicrobial action for these, polyphemusins.
About this Structure
2B5K is a Single protein structure of sequence from [1] with NH2 as ligand. Full crystallographic information is available from OCA.
Reference
Solution structure and interaction of the antimicrobial polyphemusins with lipid membranes., Powers JP, Tan A, Ramamoorthy A, Hancock RE, Biochemistry. 2005 Nov 29;44(47):15504-13. PMID:16300399
Page seeded by OCA on Wed Nov 21 08:34:21 2007
