2-keto-3-deoxygluconate transport system in Erwinia chrysanthemi

Condemine, Guy; Robert‐Baudouy, Janine

doi:10.1128/jb.169.5.1972-1978.1987

Cited by 32 publications

(19 citation statements)

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“…The phenotypes of these mutants were analyzed to check if they corresponded to already identified regulatory mutants. Two of them produced a blue pigment and thus were assumed to be pecS or pecM mutants (35) on KDG as the sole carbon source and was therefore probably a kdgR mutant (10). To confirm that the three remaining mutants did not contain new alleles of kdgR, pecS, or pecM, a kdgR::Cm r or a pecS::Cm r mutation was transduced into these mutants.…”

Section: Resultsmentioning

confidence: 99%

The Erwinia chrysanthemi pecT gene regulates pectinase gene expression

1996

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A new type of Erwinia chrysanthemi mutant displaying a derepressed synthesis of pectate lyase was isolated. The gene mutated in these strains, pecT, encodes a 316-amino-acid protein with a size of 34,761 Da that belongs to the LysR family of transcriptional activators and presents 61% identity with the E. coli protein LrhA. PecT represses the expression of pectate lyase genes pelC, pelD, pelE, pelL, and kdgC, activates pelB, and has no effect on the expression of pelA or the pectin methylesterase genes pemA and pemB. PecT activates its own expression. The mechanism by which PecT regulates pectate lyase synthesis is independent of that of the two characterized regulators of pectate lyase genes, KdgR and PecS. In contrast to most of the members of the LysR family, pecT is not transcribed in a direction opposite that of a gene that it regulates. pecT mutants are mucoid when grown on minimal medium plates and flocculate when grown in liquid minimal medium, unless leucine or alanine is added to the medium. Thus, pecT may regulate other functions in the bacterium.The synthesis and secretion of plant cell wall-degrading enzymes have been identified as one of the causes of the pathogenicity of Erwinia chrysanthemi (1). This plant pathogen is able to provoke the soft rot of a number of vegetable crops in the field or during storage. E. chrysanthemi 3937 has developed a set of enzymes to degrade pectin: two pectin methylesterases (encoded by the pemA and pemB genes) (21, 39), five major isoenzymes of pectate lyases (encoded by the pelA, pelB, pelC, pelD, and pelE genes), and at least four secondary pectate lyases. The gene of only one of them, pelL, has been cloned and studied (24). The action of these enzymes produces saturated and unsaturated oligogalacturonates that can be used as a carbon source and are metabolized by the products of the genes ogl, kduI, kduD, kdgK, and kdgA (11, 18, 33). The cellulolytic equipment of E. chrysanthemi is composed of the major, extracellular endoglucanase Z, the product of celZ (4), and of the periplasmic CelY protein, the product of celY (13).The regulation of the pel genes has been studied in vitro and in planta (23). Numerous factors influence the expression of the pel genes: growth phase (17), temperature, nitrogen starvation, oxygen concentration, osmolarity, the presence of rapidly metabolizable sugars (16), iron concentration (12), and the presence of plant extracts (5) or pectin and pectin catabolism products (8). This complexity led us to suppose that there are several regulatory proteins controlling pel gene expression. In contrast, expression of the genes of the intracellular part of the pectin degradation pathway seems to be inducible only by pectin degradation products (8), and no evidence of induction of the cel genes has been found up to now.The strategy used in our laboratory to study the regulation of the pectin degradation pathway has been to look for mutants synthesizing elevated levels of pectate lyases under uninduced conditions (17). With E. chrysanthemi 3937, this...

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Section: Resultsmentioning

confidence: 99%

The Erwinia chrysanthemi pecT gene regulates pectinase gene expression

1996

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“…Pectin is a complex heterogeneous structural polysaccharide that is a major component of the primary cell walls of all terrestrial plants (14,(16)(17)(18). Pectin can be described as a glycan matrix rich in galacturonic acid that anchors and crosslinks the load-bearing cellulosolic and hemicellulosolic fibers of the cell wall.…”

Section: Pectin Structurementioning

confidence: 99%

“…In this light, the inner membrane constitutes the final obstacle to the energy-harvesting stages of pectin utilization. Inner membrane transport is facilitated by four distinct transporters: ExuT, a symporter specific for monogalacturonate; KdgT a symporter specific for 5-keto-4-deoxyuronate, 2,5-di-keto-3-deoxygluconate, and KDG; and TogT and TogMNAB, which are specific for oligogalacturonides (1,18,29,31,32,58). Of these four independent systems, TogMNAB is the most prominent transport mechanism during pectinolysis, as the majority of monosaccharides are generated within the cytoplasm by the disaccharide oligogalacturonate lyase, Ogl (30,33).…”

Section: Intracellular Transport Is An Active and Selective Processmentioning

confidence: 99%

“…These oligogalacturonides are subsequently passaged into the cytoplasm through TogMNAB, a multisubunit CUT1 family ABC transporter that couples transport to ATP hydrolysis (1,29,32). Subsidiary transport systems, ExuT and KdgT, transport saturated and unsaturated monosaccharides, respectively (18,31,58), and TogT transports oligogalacturonides in a process that parallels the function of TogMNAB (32). Within the cell, oligogalacturonides are ultimately degraded into pyruvate and 3-phosphoglyceraldehyde, which enter the citric acid cycle and are converted into energy.…”

Section: Introductionmentioning

confidence: 99%

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Structural Biology of Pectin Degradation byEnterobacteriaceae

Abbott

Boraston

2008

Microbiol Mol Biol Rev

155

105

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SUMMARY Pectin is a structural polysaccharide that is integral for the stability of plant cell walls. During soft rot infection, secreted virulence factors from pectinolytic bacteria such as Erwinia spp. degrade pectin, resulting in characteristic plant cell necrosis and tissue maceration. Catabolism of pectin and its breakdown products by pectinolytic bacteria occurs within distinct cellular environments. This process initiates outside the cell, continues within the periplasmic space, and culminates in the cytoplasm. Although pectin utilization is well understood at the genetic and biochemical levels, an inclusive structural description of pectinases and pectin binding proteins by both extracellular and periplasmic enzymes has been lacking, especially following the recent characterization of several periplasmic components and protein-oligogalacturonide complexes. Here we provide a comprehensive analysis of the protein folds and mechanisms of pectate lyases, polygalacturonases, and carbohydrate esterases and the binding specificities of two periplasmic pectic binding proteins from Enterobacteriaceae. This review provides a structural understanding of the molecular determinants of pectin utilization and the mechanisms driving catabolite selectivity and flow through the pathway.

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“…None of the 20 E. chrysanthemi strains tested was able to use rhamnose as the sole carbon source for its growth (Table 2). In addition, no mutant able to grow on agar plates containing rhamnose as the sole carbon source was observed even after several days, in contrast to observations with lactose, 2-keto-3-deoxygluconate, or glucuronate, for which the degradation pathway exists but is not expressed in the wild-type strain (8,11,12). This suggests that E. chrysanthemi does not possess a complete rhamnose degradation pathway.…”

Section: E Chrysanthemi Secretes a Rhamnose-inducible Proteinmentioning

confidence: 40%

Rhamnogalacturonate Lyase RhiE Is Secreted by the Out System in Erwinia chrysanthemi

Laatu

Condemine

2003

J Bacteriol

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Supernatants of rhamnose-induced Erwinia chrysanthemi strain 3937 cultures contain a principal secreted protein named RhiE. A rhiE mutant has been found among a set of rhamnose-induced MudI1681 lacZ fusions. RhiE is a 62-kDa protein that has rhamnogalacturonate lyase activity on rhamnogalacturonan I (RG-I). It does not require a divalent cation for its activity and has an optimal pH of 6.0. rhiE expression is strongly induced in the presence of rhamnose but is also regulated by PecT and Crp, two regulators of the transcription of pectinolytic enzyme genes. RhiE is secreted through the type II Out secretion pathway. RhiE has no disulfide bond. The absence of RhiE secretion in a dsb mutant indicated that disulfide bond formation is required for the biogenesis of the secretion apparatus. RhiE was searched for in several E. chrysanthemi strains by using antibodies, and it was found to be present in one-third of the strains tested. However, the reduced virulence of the rhiE mutant indicates that degradation of the RG-I region of pectin is important for full virulence of E. chrysanthemi.Pectin is one of the main components present in plant cell walls. The pectin molecule can have three types of backbone: homogalacturonan, rhamnogalacturonan I (RG-I), and RG-II. Homogalacturonan (polygalacturonate [PGA]) is a polymer of galacturonic acid residues linked by ␣ 1-4 bonds which are partially methylated and acetylated. Homogalacturonan forms the smooth regions of pectin which are interspersed with hairy regions of RG-I and RG-II. RG-I has a backbone composed of as many as 100 repeats of the disaccharide ␣-L-rhamnose-␣-1,4-galacturonic acid. Side chains of arabinan or galactan are attached to O-4 of the rhamnosyl residues. RG-II is a complex polysaccharide with a short homogalacturonan backbone to which are linked side chains containing more than 10 different types of sugars (1).Plant-pathogenic microorganisms often secrete enzymes that are able to degrade the polysaccharides of cell walls in order to disorganize the plant tissue and obtain carbon sources for their growth. The enzymes that degrade the smooth regions of pectin have been extensively studied (26). The action of pectin methylesterases and of pectin acetylesterases liberates PGA. PGA is then degraded by pectate lyases or polygalacturonases that cleave either in an endo or in an exo mode. These enzymes have been characterized in bacteria as well in fungi. Much less is known about the enzymes degrading RG-I and RG-II. It seems that the presence of side chains prevents the degradation of the homogalacturonan backbone of RG-II by polygalacturonase and pectate lyases, and the debranching enzymes have not yet been characterized. Only a few enzymes that are able to cleave the RG-I backbone have so far been characterized, mostly in Aspergillus aculeatus. A rhamnogalacturonate lyase (18) cleaves inside the chain between a rhamnose and a galacturonate, creating an unsaturation on the galacturonate at the nonreducing end. A rhamnogalacturonate rhamnohydrolase (17) and a rha...

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2-keto-3-deoxygluconate transport system in Erwinia chrysanthemi

Cited by 32 publications

References 29 publications

The Erwinia chrysanthemi pecT gene regulates pectinase gene expression

The Erwinia chrysanthemi pecT gene regulates pectinase gene expression

Structural Biology of Pectin Degradation byEnterobacteriaceae

Rhamnogalacturonate Lyase RhiE Is Secreted by the Out System in Erwinia chrysanthemi

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