bacteriocins Flashcards
defn bacteriocins
Diverse group of robosomally synthesized antimicrobial peptides produced by bacteria
attributes
heat stable, active at low concentrations
function
signalling and repelling, colonizing peptides,narrow spectrum of activety which is effective against closely related bacterial strains
Class 1 Bacteriocins
aka lantibiotics
eg nisin E234 and lacticin 3147. Which are gram positive
Post- Translationally modified peptides
synthesis of peptides C- N ( Carboxyl to N-terminus) core peptides is post translationally modidied and contains dehydrated a.a such as serine and threoinine + 5 methyl- lanthionine rings.The leader peptide ensures NisA remains inactive until translocation of intracellular space and leader peptide is cleaved off and it becomes active nisin
How do class 1 work
Nisin binds to Lipid 2 which transports cell wall subunits through membrane. This causes pore formation into cell membrane leading to membrane depolarization and permeabilization which leads to cell death
How does lacticin 3147 work
acts with 2 peptides Ltn A and LtnB which works synergistically. Ltna binds to precursors of peptidoglycan production ( lipid 2) while LtnB reacts with the complex. Located on conjugative plasmid
class 2
Sakacin P
small thermostable peptides
active at low concentration
how do class 2 work
usues and binds to protein receptors, upon binding it induces formation of spores (poke holes) into the cell membrane of target m.o which results in cell disruption and cell death.
Sakacin P structure
hydrophillic outside, hydrophobic core membrane. the N-terminal B-sheet domain mediates the binding. C-terminal hairpin domain- determines target cell specificity.
class 2 target
listeria
class 3
large heat labile enzymes with a narrow host change
target
staphylococcus aureus
how do class 3 work
they hydrolysise the peptidoglycan layer leading to cell lysis
class 3 bacteriocin !!!
Lysostaphin is an ENZYME
