Transmembrane transport of peptidoglycan precursors across model and bacterial membranes.
Translocation of the peptidoglycan precursor Lipid II across the cytoplasmic membrane is a key step in bacterial cell wall synthesis, but hardly understood. Using NBD-labelled Lipid II, we showed by fluorescence and TLC assays that Lipid II transport does not occur spontaneously and is not induced by the presence of single spanning helical transmembrane peptides that facilitate transbilayer movement of membrane phospholipids. MurG catalysed synthesis of Lipid II from Lipid I in lipid vesicles also did not result in membrane translocation of Lipid II. These findings demonstrate that a specialized protein machinery is needed for transmembrane movement of Lipid II. In line with this, we could demonstrate Lipid II translocation in isolated Escherichia coli inner membrane vesicles and this transport could be uncoupled from the synthesis of Lipid II at low temperatures. The transport process appeared to be independent from an energy source (ATP or proton motive force). Additionally, our studies indicate that translocation of Lipid II is coupled to transglycosylation activity on the periplasmic side of the inner membrane.
van Dam
Vincent
V
Department Biochemistry of Membranes, Bijvoet Centre, Utrecht University, 3584 CH, Utrecht, The Netherlands. v.vandam@chem.uu.nl
Sijbrandi
Robert
R
Kol
Matthijs
M
Swiezewska
Ewa
E
de Kruijff
Ben
B
Breukink
Eefjan
E
D001393:Azoles / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism*; D002855:Chromatography, Thin Layer; D003080:Cold Temperature; D004926:Escherichia coli / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000494:pharmacology; D026901:Membrane Transport Proteins / Q000378:metabolism*; D009578:Nitrobenzenes / Q000494:pharmacology; D046928:Peptidoglycan Glycosyltransferase / Q000378:metabolism; D013194:Staining and Labeling; D014538:Uridine Diphosphate N-Acetylmuramic Acid / Q000031:analogs & derivatives* / Q000378:metabolism
C510797:7-nitrobenz-2-oxa-1,3-diazol-4-yl; D001393:Azoles; D005456:Fluorescent Dyes; D026901:Membrane Transport Proteins; D009578:Nitrobenzenes; D014538:Uridine Diphosphate N-Acetylmuramic Acid; C069249:muramyl-NAc-(pentapeptide)pyrophosphoryl-undecaprenol; D046928:Peptidoglycan Glycosyltransferase