title: Discovery of new biosynthetic pathways: the lipid A story.
abstract: The outer monolayer of the outer membrane of Gram-negative bacteria consists of the lipid A component of lipopolysaccharide (LPS), a glucosamine-based saccharolipid that is assembled on the inner surface of the inner membrane. The first six enzymes of the lipid A pathway are required for bacterial growth and are excellent targets for the development of new antibiotics. Following assembly, the ABC transporter MsbA flips nascent LPS to the periplasmic side of the inner membrane, whereupon additional transport proteins direct it to the outer surface of the outer membrane. Depending on the bacterium, various covalent modifications of the lipid A moiety may occur during the transit of LPS to the outer membrane. These extra-cytoplasmic modification enzymes are therefore useful as reporters for monitoring LPS trafficking. Because of its conserved structure in diverse Gram-negative pathogens, lipid A is recognized as foreign by the TLR4/MD2 receptor of the mammalian innate immune system, resulting in rapid macrophage activation and robust cytokine production.
authors.affiliation: Department of Biochemistry, Duke University Medical Center, P.O. Box 3711, Durham, NC 27710, USA. raetz@biochem.duke.edu
authors.forename: Christian R H
authors.initials: CR
authors.lastname: Raetz
authors.forename: Ziqiang
authors.initials: Z
authors.lastname: Guan
authors.forename: Brian O
authors.initials: BO
authors.lastname: Ingram
authors.forename: David A
authors.initials: DA
authors.lastname: Six
authors.forename: Feng
authors.initials: F
authors.lastname: Song
authors.forename: Xiaoyuan
authors.initials: X
authors.lastname: Wang
authors.forename: Jinshi
authors.initials: J
authors.lastname: Zhao
mesh_terms: D000217:Acyltransferases / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D005603:Francisella / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007113:Immunity, Innate / Q000276:immunology; D008050:Lipid A / Q000096:biosynthesis* / Q000737:chemistry / Q000276:immunology
chemical_list: D008050:Lipid A; D000217:Acyltransferases; C050304:acyl-(acyl-carrier-protein)-UDP-N-acetylglucosamine acyltransferase