Three-Dimensional Structure of Leucocin A in Trifluoroethanol and Dodecylphosphocholine Micelles:  Spatial Location of Residues Critical for Biological Activity in Type IIa Bacteriocins from Lactic Acid Bacteria^,

Abstract

The first three-dimensional structure of a type IIa bacteriocin from lactic acid bacteria is reported. Complete 1 H resonance assignments of leucocin A, a 37 amino acid antimicrobial peptide isolated from the lactic acid bacterium Leuconostoc gelidum UAL187, were determined in 90% trifluoroethanol (TFE)water and in aqueous dodecylphosphocholine (DPC) micelles (1:40 ratio of leucocin A:DPC) using twodimensional NMR techniques (e.g., DQF-COSY, TOCSY, NOESY). Circular dichroism spectra, NMR chemical shift indices, amide hydrogen exchange rates, and long-range nuclear Overhauser effects indicate that leucocin A adopts a reasonably well defined structure in both TFE and DPC micelle environments but exists as a random coil in water or aqueous DMSO. Distance geometry and simulated annealing calculations were employed to generate structures for leucocin A in both lipophilic media. While some differences were noted between the structures calculated for the two different solvent systems, in both, the region encompassing residues 17-31 assumes an essentially identical amphiphilic R-helix conformation. A three-strand antiparallel β-sheet domain (residues 2-16), anchored by the disulfide bridge, is also observed in both media. In TFE, these two regions have a more defined relationship relative to each other, while, in DPC micelles, the C-terminus is folded back onto the R-helix. The implications of these structural features with regard to the antimicrobial mechanism of action and target recognition are discussed. † These investigations were supported by the Natural Sciences and Engineering Research Council of Canada.‡ Coordinates of leucocin A in TFE and DPC micelles have been deposited in the Brookhaven Protein Data Bank (filenames 2leu and 3leu, respectively).

Characterization of the Antimicrobial Peptide Penisin, a Class Ia Novel Lantibiotic from Paenibacillus sp. Strain A3

“…Thus, they do not exhibit any conformation-related obligations while present inside the host. The structures of several lantibiotics, like nisin, mutacin, epilancin, and leucocin A, have been elucidated using CD and NMR (45)(46)(47)(48)(49)(50)(51). Although antimicrobial peptides have attracted increasing attention over the last 2 decades, issues such as nonspecific cytotoxicity, hemolysis (7), and poor efficiency under in vivo conditions have limited their clinical utility (52).…”

Novel Activator of Mannose-Specific Phosphotransferase System Permease Expression in Listeria innocua , Identified by Screening for Pediocin AcH Resistance

“…Class IIa bacteriocins (also known as YGNGV bacteriocins) have a common secondary structure (19,48,51) and mechanism of action (16). Initially, these peptides are thought to bind to negatively charged molecules, such as teichoic acids in the cell wall (7).…”

“…Subsequently, they transfer to the cytoplasmic membrane, where they interact with anionic phospholipids (9) and a phosphoenolpyruvate-dependent phosphotransferase system (PTS) permease of the mannose structural family (EII t Man ) (38). Once they are bound to cell membranes, class IIa bacteriocins fold into a ␤␣ conformation (19,48,51) in which the nonpolar ␣-helical region is inserted into the phospholipid bilayer (32). Ultimately, ion conductance pores are formed, resulting in cell death due to the dissipation of the membrane electrochemical gradient (10).…”

Variations in the Membrane Fatty Acid Composition of Resistant or Susceptible Leuconostoc or Weissella Strains in the Presence or Absence of Mesenterocin 52A and Mesenterocin 52B Produced by Leuconostoc mesenteroides subsp. mesenteroides FR52

“…This peptide is atypical, because no class II subclass corresponds to it. The amphipathic and cationic characters and ␣-helix conformation of these peptides are related to their mechanism of action, with the cell membrane as the primary target (3,9,10).…”