title: A two-component Kdo hydrolase in the inner membrane of Francisella novicida.
abstract: Lipid A coats the outer surface of the outer membrane of Gram-negative bacteria. In Francisella tularensis subspecies novicida lipid A is present either as the covalently attached anchor of lipopolysaccharide (LPS) or as free lipid A. The lipid A moiety of Francisella LPS is linked to the core domain by a single 2-keto-3-deoxy-D-manno-octulosonic acid (Kdo) residue. F. novicida KdtA is bi-functional, but F. novicida contains a membrane-bound Kdo hydrolase that removes the outer Kdo unit. The hydrolase consists of two proteins (KdoH1 and KdoH2), which are expressed from adjacent, co-transcribed genes. KdoH1 (related to sialidases) has a single predicted N-terminal transmembrane segment. KdoH2 contains 7 putative transmembrane sequences. Neither protein alone catalyses Kdo cleavage when expressed in E. coli. Activity requires simultaneous expression of both proteins or mixing of membranes from strains expressing the individual proteins under in vitro assay conditions in the presence of non-ionic detergent. In E. coli expressing KdoH1 and KdoH2, hydrolase activity is localized in the inner membrane. WBB06, a heptose-deficient E. coli mutant that makes Kdo(2) -lipid A as its sole LPS, accumulates Kdo-lipid A when expressing the both hydrolase components, and 1-dephospho-Kdo-lipid A when expressing both the hydrolase and the Francisella lipid A 1-phosphatase (LpxE).
authors.affiliation: Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Jinshi
authors.initials: J
authors.lastname: Zhao
authors.forename: Christian R H
authors.initials: CR
authors.lastname: Raetz
mesh_terms: D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins; D005604:Francisella tularensis / Q000201:enzymology* / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000235:genetics* / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; C043426:inner membrane protein, E coli; D006026:Glycoside Hydrolases