Interaction of divalent cations and polymyxin B with lipopolysaccharide

Schindler, Melvin; Osborn, Mary

doi:10.1021/bi00587a024

Cited by 315 publications

(250 citation statements)

References 31 publications

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“…G. sulfurreducens produces a rough LPS, i.e., it is composed of lipid A and a core oligosaccharide but lacks the O antigen (45). The core oligosaccharide is the most highly charged region of the LPS and is stabilized by metallic cations (46). Models suggest that rough LPS preferentially chelates and immobilizes uranyl ions over other ions (32) and produces carboxyl and hydroxyl coordinations (32), which is consistent with the C and O coordinations modeled from the EXAFS spectra.…”

Section: Discussion Physiological Relevance Of the Extracellular Redusupporting

confidence: 63%

Extracellular reduction of uranium via Geobacter conductive pili as a protective cellular mechanism

Cologgi

Lampa-Pastirk

Speers

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

218

239

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The in situ stimulation of Fe(III) oxide reduction by Geobacter bacteria leads to the concomitant precipitation of hexavalent uranium [U(VI)] from groundwater. Despite its promise for the bioremediation of uranium contaminants, the biological mechanism behind this reaction remains elusive. Because Fe(III) oxide reduction requires the expression of Geobacter 's conductive pili, we evaluated their contribution to uranium reduction in Geobacter sulfurreducens grown under pili-inducing or noninducing conditions. A pilin-deficient mutant and a genetically complemented strain with reduced outer membrane c -cytochrome content were used as controls. Pili expression significantly enhanced the rate and extent of uranium immobilization per cell and prevented periplasmic mineralization. As a result, pili expression also preserved the vital respiratory activities of the cell envelope and the cell's viability. Uranium preferentially precipitated along the pili and, to a lesser extent, on outer membrane redox-active foci. In contrast, the pilus-defective strains had different degrees of periplasmic mineralization matching well with their outer membrane c -cytochrome content. X-ray absorption spectroscopy analyses demonstrated the extracellular reduction of U(VI) by the pili to mononuclear tetravalent uranium U(IV) complexed by carbon-containing ligands, consistent with a biological reduction. In contrast, the U(IV) in the pilin-deficient mutant cells also required an additional phosphorous ligand, in agreement with the predominantly periplasmic mineralization of uranium observed in this strain. These findings demonstrate a previously unrecognized role for Geobacter conductive pili in the extracellular reduction of uranium, and highlight its essential function as a catalytic and protective cellular mechanism that is of interest for the bioremediation of uranium-contaminated groundwater.

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Section: Discussion Physiological Relevance Of the Extracellular Redusupporting

confidence: 63%

Extracellular reduction of uranium via Geobacter conductive pili as a protective cellular mechanism

Cologgi

Lampa-Pastirk

Speers

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

218

239

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“…Earlicr data from our laboratory [4], as well as that of Schindler and Osborn [5], suggested that polymyxin B binding to LPS occurred primarily via ionic interactions, whereas our more recent data [l, 21 have implicated hydrophobic interactions as dictating lysozyme binding to LPS. We therefore investigated the combined effects of lysozyme and polymyxin B on binding to LPS.…”

Section: Independent Lps-binding Siie Specificities For Lysozyme Andmentioning

confidence: 70%

Effects of lipopolysaccharide chemotype structure on binding and inactivation of hen egg lysozyme

Ohno

Morrison

1989

European Journal of Biochemistry

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The structural features of lipopolysaccharide [LPS] which influence the binding and inactivation of lysozyme have been examined. Binding of polysaccharide-containing LPS (S-LPS) and Ra -Rc-LPS preparations was independent of temperature between 37 ~ 50°C; in contrast, binding of Rd-LPS, Re-LPS and lipid A was temperature-dependent. The binding of lysozyme to Rd-LPS and Re-LPS was increased by treatment with mild alkali, which has little detectable effect on binding of lysozyme to S-LPS and Ra -Rc-LPS preparations.Competitive binding experiments using dansylated lysozyme and/or daiisylated polymyxin B indicated independent binding sites on the LPS for lysozyme and polymyxin B. These results indicate significant differences between most LPS preparations and lipid A and glycolipid 1 ,PS in their interaction with proteins of maminalian origin.Previous studies from this laboratory have demonstrated a high-affinity binding of lysozyine from a variety of mammalian sources to bactcrial lipopolysaccharides (LPS), resulting in reversible inhibition of the enzymatic activity of lysozynie [I]. The major binding sites on lysozyme responsiblc for LPS association were two negatively charged hydrophobic regions of the lysozyme associated with the catalytically active site [l. 21. Our results indicated hydrophobic binding to be a major contributing fkctor t o the interaction, and thus implicated the lipid A region of LPS as responsible for lysozyme binding. Our data also suggested, howevcr, that both purified lipid A and LPS from the deep rough Sulmonellu minnesota Re strain were significantly less elficient in binding to lysozyme in comparison to S-LPS arid Ra -Rc-LPS preparations. Since the former preparations contain significantly more lipid A on a percentage by mass basis than the latter (see Fig. I), these results are not consistent with lipid A being the dominant binding site on LPS for lysozyme. We have, thcrcfore, carried out additional experiments to characterize structural relationships of LPS which contribute to the interactions between LPSjlipid A and lysozyme. The results of these studies suggcst that the structure of LPS influences its binding to lysozyine. The Rd and Re chcmotypc LPS and lipid A less readily bind lysozyme in comparison to S-LPS or Ra -Rc-LPS; howcvcr, binding of the former preparations can bc increased at mildly elevated temperatures (e.g. 50°C) or by mild alkaline hydrolysis. Neither of these procedurcs increases binding of S-LPS or Ra-Rc-LPS to lysozyme. These results suggest that availability of lysozyme binding domains on the LPS may, in the case of lipid A, Rd-LPS and Re-LPS, require tcmperaturedependent changes and/or chemical modification.

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“…The R. etli and R. leguminosarum common inner core contains Kdo, mannose, galactose, and an abundance of galacturonic acid, the latter probably serving as a substitute for phosphate found in the enteric LPS core regions. The resulting inner core would have a high negative charge density, allowing the LPS to stabilize in the membrane in the presence of Ca 2ϩ and other divalent cations, such as proposed for the enteric LPS inner cores (42,43). It is well documented that pectic polysaccharides rich in GalA exhibit a high degree of cross-linking in the presence of Ca 2ϩ (44).…”

Section: Discussionmentioning

confidence: 99%

The Structures of the Lipopolysaccharides from Rhizobium etli Strains CE358 and CE359

Forsberg

Carlson

1998

Journal of Biological Chemistry

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The structural arrangement of oligosaccharides comprising the core region of Rhizobium etli CE3 lipopolysaccharide (LPS) has been elucidated through the characterization of the LPSs from two R. etli mutants. One mutant, CE358, completely lacks the O-chain polysaccharide, while the second mutant, CE359, contains a truncated portion of this polysaccharide. This structural arrangement of the core oligosaccharides in these LPSs was determined using electrospray ionization mass spectrometry, tandem mass spectrometry, and methylation analysis. Mild acid hydrolysis of the CE359 LPS produces two major core oligosaccharides: a tetrasaccharide (1) with the structure ␣-D-Galp- (136) Bacteria belonging to the family Rhizobiaceae are Gram-negative and are able to form nitrogen-fixing symbiotic relationships with legume plants. The surface polysaccharides, including the lipopolysaccharides (LPSs), 1 are involved in the normal infection process. Mutants that lack the O-chain polysaccharide portion of their LPSs are symbiotically defective in that they are unable to form normal infection threads (1, 2), and/or they cannot invade the root nodule cells (3-5). In addition, it has been shown that structural changes in the LPS occur during symbiotic infection and that most of these changes appear to take place in the O-chain polysaccharide portion of the LPS (6 -14). These structural adaptations in response to the environment of the host plant are likely to be important in order for the symbiont bacterium to induce a nitrogen-fixing nodule.In addition to the importance of determining the symbiotic "virulence" of these bacteria, rhizobial LPSs can have unique structural features compared with the LPSs from enteric bacteria. The most studied LPSs, the topic of this report, are those from Rhizobium etli and Rhizobium leguminosarum. All of the LPSs examined from wild-type or parent strains of these species are devoid of phosphate. Their lipid A region has a trisaccharide backbone consisting of one each of galacturonosyl (GalA), GlcN, and 2-aminogluconosyl (GlcN-onate) residues, the latter two residues being O-and N-acylated with ␤-hydroxy fatty acids and one very long chain fatty acid, 27-hydroxyoctacosanoic acid (15). This lipid A also appears not to carry any acyloxylacyl substituents. The core region has been found to consist of two oligosaccharides (16, 17) as shown below.

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Interaction of divalent cations and polymyxin B with lipopolysaccharide

Cited by 315 publications

References 31 publications

Extracellular reduction of uranium via Geobacter conductive pili as a protective cellular mechanism

Extracellular reduction of uranium via Geobacter conductive pili as a protective cellular mechanism

Effects of lipopolysaccharide chemotype structure on binding and inactivation of hen egg lysozyme

The Structures of the Lipopolysaccharides from Rhizobium etli Strains CE358 and CE359

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