title: Characterization of Pseudomonas aeruginosa LpxT reveals dual positional lipid A kinase activity and co-ordinated control of outer membrane modification.
abstract: Gram-negative bacteria have evolved modification machinery to promote a dynamic outer membrane in response to a continually fluctuating environment. The kinase LpxT, for example, adds a phosphate group to the lipid A moiety of some Gram-negatives including Escherichia coli and Salmonella enterica. LpxT activity is inhibited under conditions that compromise membrane integrity, resulting instead in the addition of positively charged groups to lipid A that increase membrane stability and provide resistance to cationic antimicrobial peptides. We have now identified a functional lpxT orthologue in P. aeruginosa. LpxTPa has unique enzymatic characteristics, as it is able to phosphorylate P. aeruginosa lipid A at two sites of the molecule. Surprisingly, a previously uncharacterized lipid A 4'-dephospho-1-triphosphate species was detected. LpxTPa activity is inhibited by magnesium independently of lpxTPa transcription. Modulation of LpxTPa activity is influenced by transcription of the lipid A aminoarabinose transferase ArnT, known to be activated in response to limiting magnesium. These results demonstrate a divergent activity of LpxTPa , and suggest the existence of a co-ordinated regulatory mechanism that permits adaptation to a changing environment.
authors.affiliation: Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas, USA.
authors.forename: Emily M
authors.initials: EM
authors.lastname: Nowicki
authors.forename: John P
authors.initials: JP
authors.lastname: O'Brien
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Brodbelt
authors.forename: M Stephen
authors.initials: MS
authors.lastname: Trent
mesh_terms: D002462:Cell Membrane / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000378:metabolism; D006602:Hexosyltransferases / Q000378:metabolism; D008050:Lipid A / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism; D017856:Phosphotransferases (Phosphate Group Acceptor) / Q000378:metabolism*; D011550:Pseudomonas aeruginosa / Q000201:enzymology*
chemical_list: D004791:Enzyme Inhibitors; D008050:Lipid A; D006602:Hexosyltransferases; D017856:Phosphotransferases (Phosphate Group Acceptor); D008274:Magnesium