1. THE PEPTIDE GROUP AT IBV
STRUCTURE AND MODE-OF-ACTION OF PEPTIDE BACTERIOCINS/ANTIMICROBIAL PEPTIDES (AMPs)
THE PEPTIDE GROUP AT IBV
Tom Kristensen Professor
Jon Nissen-Meyer Professor
Bie Ekblad Stipendiat
Randi Ose Ing.
Close collaboration with
Per Eugen Kristiansen (at IBV)
Laboratory of Microbial Gene Technology, NMBU (Dzung B. Diep and Ingolf F. Nes)

2. The bacteriocins have been isolated, sequenced and the genes required for production identified/sequenced
At least four genes/proteins are necessary for production of bacteriocins
The gene encoding the bacteriocin
Immunity gene/protein
Dedicated ABC-transporter for bacteriocin secretion
Accessory protein/gene
The Pediocin PA-1 Accessory Protein Ensures Correct Disulfide Bond Formation in the Antimicrobial Peptide Pediocin PA-1

3. These AMPs/bacteriocins permeabilize and kill bacteria at pico-to nano-molar concentrations
Their immunity proteins protect bacteria from being killed by AMPs
The AMPs act as peptide ligands: i.e. they bind specifically to cell-surface receptors, thus causing structural changes in the receptors, which then leads to membrane leakage. The immunity proteins bind to the receptors and prevent membrane leakage.

4. The structure of LcnA-immunity protein determined by NMR-spectroscopy
The group uses NMR-spectroscopy, X-ray crystallography, MDS and SD-mutagenesis to determine protein structures
The structure of Ped-immunity protein determined by X-ray crystallography
The structure of LcnA-immunity protein determined by NMR-spectroscopy
Sakacin
Curvacin
Lactococcin-G
Plantaricin-EF
Plantaricin-A
NMR 3D-structures of five antibacterial peptides determined by the group

5. X The mode-of-action of bacteriocins Hydrophobic core of membrane
Hydrophilic outside
Membrane interface
Hydrophobic core
of membrane X
Flux of molecules out of cell
Flux of molecules out of cell
Membrane interface
Receptor
Receptor
Innside cell
Receptors have been identified by whole genome sequencing of resistant and sensitive cells
Immunity protein
The mode-of-action of bacteriocins

6. The 3D-structures of five antimicrobial peptides
The 3D structure of two immunity proteins
The 3D-structures of five antimicrobial peptides