Biochemistry and Physiology of Hopanoids in Bacteria

Sahm, Hermann; Rohmer, Michel; Bringer-Meyer, Stephanie; Sprenger, Georg A.; Welle, Roland

doi:10.1016/s0065-2911(08)60100-9

Cited by 68 publications

(40 citation statements)

References 97 publications

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“…Different rates of glucose uptake in Z. mobilis have been estimated by microcalorimetry at 30ЊC (816 nmol min Ϫ1 mg Ϫ1 of cells [7]), by application of a two-point kinetics at 30ЊC (200 to 300 nmol min Ϫ1 mg Ϫ1 of protein [10]), and by measurement of glucose consumption rates (1,800 nmol min Ϫ1 mg Ϫ1 [dry weight] [7]). Although comparable activities were determined in the present study, it is not known whether the levels of gene expression in the two organisms are in a similar range, whether insertion into the membrane is equally efficient, and to what extent the different membrane compositions (19) affect the carrier activity.…”

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confidence: 54%

Functional expression of the glucose transporter of Zymomonas mobilis leads to restoration of glucose and fructose uptake in Escherichia coli mutants and provides evidence for its facilitator action

et al. 1995

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The Zymomonas mobilis genes encoding the glucose facilitator (glf), glucokinase (glk), or fructokinase (frk) were cloned and expressed in a lacI q -Ptac system using Escherichia coli K-12 mutants deficient in uptake and phosphorylation of glucose and fructose. Growth on glucose or fructose was restored when the respective genes (glf-glk or glf-frk) were expressed. In E. coli glf ؉ strains, both glucose and fructose were taken up via facilitated diffusion (K m , 4.1 mM for glucose and 39 mM for fructose; V max at 15؇C, 75 and 93 nmol min ؊1 mg ؊1 [dry weight] for glucose and fructose, respectively). For both substrates, counterflow maxima were observed.Glucose can be transported in bacteria by carrier systems which belong either to the phosphoenolpyruvate-dependent phosphotransferase system (PTS) type, to proton-or cationlinked permeases, or to ATP-binding cassette (ABC)-type carriers (4, 17). A rare case is the facilitator-type transport (uniport) of glucose in bacteria, exemplified by the system of the gram-negative, strictly fermentative bacterium Zymomonas mobilis. This type of sugar uptake does not use metabolic energy in the form of a proton potential or phosphoenolpyruvate (10, 17). Biochemical evidence for facilitated diffusion of glucose in this organism came from earlier studies (10, 26) and from in vivo nuclear magnetic resonance measurements using 13 C-labeled glucose and xylose as substrates (22). Mainly on the basis of competition studies, it was stated that the glucose facilitator (GLF) of Z. mobilis is a low-affinity, high-velocity carrier which in addition to glucose also transports fructose, xylose, or nonmetabolizable glucose analogs, such as 2-deoxyglucose (10,22,26). The sequence of a presumptive glf gene from Z. mobilis was reported (6), and on the basis of sequence comparison, this open reading frame was found to be a member of a superfamily of sugar transporters from both prokaryotes and eukaryotes (for a recent review, see reference 3). Recently, it was shown that the glf plus glk genes of Z. mobilis complemented an Escherichia coli mutant strain, which was deficient in glucokinase and in glucose uptake, to growth on glucose (23). However, detailed glucose uptake studies using this heterologous system have not yet been reported, nor was the substrate range of this carrier studied further.Plasmid constructions. DNA preparation, cloning, restriction analysis, and transformation were done according to established methods (20). Chromosomal DNA from Z. mobilis ZM6 (27) was prepared according to the lysozyme freeze-thaw method (12). The Z. mobilis gene glf from strain CP4 (15) had been fortuitously cloned in our laboratory as a 2.3-kb HindIII DNA fragment (pZY600) and shown to confer Glf activity to E. coli Glc Ϫ strains (18). DNA sequencing established the identity with the glf sequence reported earlier (6). The glf gene was amplified by PCR (16) using plasmid pZY600 as a template, and glk (6) and frk (31) genes were amplified from chromosomal DNA of Z. mobilis ZM6. The PCR primers for glf wer...

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confidence: 54%

Functional expression of the glucose transporter of Zymomonas mobilis leads to restoration of glucose and fructose uptake in Escherichia coli mutants and provides evidence for its facilitator action

et al. 1995

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“…Some bacteria may have other mechanisms to avoid the loss of these particles. Hopanoid concentrations are greatest in acidophiles and are found almost exclusively in membranes containing large proton gradients (19,31,59). Thus, hopanoids may be able to increase the packing of the hydrophobic centers in lipid bilayers, preventing the loss of protons as charged water (19).…”

Section: Discussionmentioning

confidence: 99%

Hopanoid Production Is Required for Low-pH Tolerance, Antimicrobial Resistance, and Motility in Burkholderia cenocepacia

2011

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Hopanoids are pentacyclic triterpenoids that are thought to be bacterial surrogates for eukaryotic sterols, such as cholesterol, acting to stabilize membranes and to regulate their fluidity and permeability. To date, very few studies have evaluated the role of hopanoids in bacterial physiology. The synthesis of hopanoids depends on the enzyme squalene-hopene cyclase (Shc), which converts the linear squalene into the basic hopene structure. Deletion of the 2 genes encoding Shc enzymes in Burkholderia cenocepacia K56-2, BCAM2831 and BCAS0167, resulted in a strain that was unable to produce hopanoids, as demonstrated by gas chromatography and mass spectrometry. Complementation of the ⌬shc mutant with only BCAM2831 was sufficient to restore hopanoid production to wild-type levels, while introducing a copy of BCAS0167 alone into the ⌬shc mutant produced only very small amounts of the hopanoid peak. The ⌬shc mutant grew as well as the wild type in medium buffered to pH 7 and demonstrated no defect in its ability to survive and replicate within macrophages, despite transmission electron microscopy (TEM) revealing defects in the organization of the cell envelope. The ⌬shc mutant displayed increased sensitivity to low pH, detergent, and various antibiotics, including polymyxin B and erythromycin. Loss of hopanoid production also resulted in severe defects in both swimming and swarming motility. This suggests that hopanoid production plays an important role in the physiology of B. cenocepacia.

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“…The five-ring triterpene structures called hopanoids are ancient and have been identified as the main membrane-lipid support in a number of prokaryotes that evolved before the rise in atmospheric oxygen, when synthesis of sterols became possible (45). Hopanoids have a fascinating property of preventing the inward leakage of protons (46), which could contribute to a decrease in oxidative stress.…”

Section: Figurementioning

confidence: 99%

Triterpenoid electrophiles (avicins) activate the innate stress response by redox regulation of a gene battery

Haridas¹,

Hanausek²,

Nishimura³

et al. 2004

J. Clin. Invest.

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Avicins are proapoptotic and anti-inflammatory triterpene electrophiles isolated from an Australian desert tree, Acacia victoriae. The presence of two α,β unsaturated carbonyl groups (Michael reaction sites) in the side chain of the avicin molecule prompted us to study its effects on NF-E2–related factor 2 (Nrf2), a redox-regulated transcription factor that controls the expression of a battery of detoxification and antioxidant proteins via its binding to antioxidant response element (ARE). Avicin D–treated Hep G2 cells showed translocation of Nrf2 into the nucleus and a time-dependent increase in ARE activity. These properties were sensitive to DTT, suggesting that avicins affect one or more critical cysteine residues, probably on the Keap1 molecule. Downstream of ARE, an activation of a battery of stress-induced proteins occurred. The implications of these findings were evaluated in vivo in mouse skin exposed to an ancient stressor, UV light. Avicins inhibited epidermal hyperplasia, reduced p53 mutation, enhanced apoptosis, decreased generation of 8-hydroxy-2′-deoxyguanosine, and enhanced expression of NADPH:quinone oxidoreductase 1 and heme oxygenase-1. These data, combined with our earlier published work, demonstrate that avicins represent a new class of plant stress metabolites capable of activating stress adaptation and suppressing proinflammatory components of the innate immune system in human cells by redox regulation. The relevance for treatment of clinical diseases in which stress responses are dysfunctional or deficient is discussed

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Biochemistry and Physiology of Hopanoids in Bacteria

Cited by 68 publications

References 97 publications

Functional expression of the glucose transporter of Zymomonas mobilis leads to restoration of glucose and fructose uptake in Escherichia coli mutants and provides evidence for its facilitator action

Functional expression of the glucose transporter of Zymomonas mobilis leads to restoration of glucose and fructose uptake in Escherichia coli mutants and provides evidence for its facilitator action

Hopanoid Production Is Required for Low-pH Tolerance, Antimicrobial Resistance, and Motility in Burkholderia cenocepacia

Triterpenoid electrophiles (avicins) activate the innate stress response by redox regulation of a gene battery

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