William T. Doerrler
William T. DoerrlerWe are interested in the biogenesis of the outer membrane (OM) of the model Gram-negative bacteria Escherichia coli. The envelope of E. coli contains two distinct membranes, an inner membrane and outer membrane, separated by the peptidoglycan-containing periplasmic space. The inner, or cytoplasmic, membrane is a phospholipid bilayer containing proteins involved in signaling, protein export, nutrient uptake, ATP synthesis and other functions. The OM is an asymmetric lipid bilayer consisting of an inner leaflet of phospholipids and an outer leaflet of lipopolysaccharide (LPS). LPS is a complex glycolipid that contributes to the remarkable permeability barrier provided by the OM and is a potent stimulator of the mammalian innate immune response via its activation of Toll-like receptors. The OM also contains a variety of integral membrane proteins that adopt a beta-barrel conformation and are involved in solute uptake and other functions. The components of the OM are synthesized in the cytoplasm using cytoplasmic precursors and enzymes. OM lipids are transported across the IM following synthesis by MsbA. MsbA is an ATP binding cassette (ABC) transporter family member that is highly conserved across evolution.
The assembly of these transported molecules into a functional OM is the focus of our work. YaeT, a highly conserved OM protein, may play a role in assembly of proteins into the OM. A YaeT conditional mutant appears to lose newly synthesized and existing OM proteins upon shift to nonpermissive conditions. Since the proteins mentioned above are found in all Gram-negative bacteria, OM biogenesis likely occurs through a similar process in other Gram-negative pathogens. This pathway may represent a promising target for the development of novel antibiotics.
Bacterial biofilms are surface associated communities that pose important medical problems due to resistance to antibiotics and cleaning and sterilizing agents. In a collaborative effort with the biotech industry, we are screening a library of novel compounds for their ability to inhibit formation of and disrupt existing biofilms of Pseudomonas aeruginosa.
Selected Publications:
Doerrler WT. Lipid trafficking to the outer membrane of Gram-negative bacteria. Molecular Microbiology. 60; 542-552, 2006.
Doerrler WT. and Raetz CR. Loss of outer membrane proteins without inhibition of lipid export in an Escherichia coli YaeT mutant. J Biol Chem. 280; 27679-87, 2005.
Doerrler WT., Gibbons HS, Raetz CR. MsbA-dependent translocation of lipids across the inner membrane of Escherichia coli. J Biol Chem. 279; 45102-9, 2004.
Doerrler WT. and Raetz CR. ATPase activity of the MsbA lipid flippase of Escherichia coli. J Biol Chem 277; 36697-36705, 2002.
Doerrler WT., Reedy MC, Raetz CR. An Escherichia coli mutant defective in lipid export. J Biol Chem 276; 11461-11464, 2001.
Doerrler WT. and Lehrman MA. Regulation of the dolichol pathway in human fibroblasts by the endoplasmic reticulum unfolded protein response. Proc Nat Acad Sci USA 96; 13050-13055, 1999.
Doerrler WT., Ye J, Falck JR, Lehrman MA. Acylation of glucosaminyl phosphatidylinositol revisited. Palmitoyl-CoA dependent palmitoylation of the inositol residue of a synthetic dioctanoyl glucosaminyl-phosphatidylinositol by hamster membranes permits efficient mannosylation of the glucosamine residue. J Biol Chem 271; 27031-27038, 1996.
