Disulfide bridges in tomato pectinesterase: Variations from pectinesterases of other species; conservation of possible active site segments

Markovič, Oskar; Jörnvall, Hans

doi:10.1002/pro.5560011007

Cited by 35 publications

(13 citation statements)

References 13 publications

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“…Turns T2 and T3 are generally longer and more variable; in particular, TF3 and most of T2 turns protrude from the central parallel b-helix to form the shallow cleft where the putative active site is located. In contrast with what was reported (Markovic and Jornvall, 1992), no electron density corresponding to the disulphide bridges Cys98-Cys125 and Cys166-Cys200 was observed. The absence of these bridges was confirmed by biochemical analysis, indicating the presence of four thiol groups upon titration with the Ellman's reagent in denaturing conditions (data not shown).…”

Section: Resultscontrasting

confidence: 99%

Structural Basis for the Interaction between Pectin Methylesterase and a Specific Inhibitor Protein

Matteo¹,

Giovane

Raiola³

et al. 2005

Plant Cell

206

224

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Pectin, one of the main components of the plant cell wall, is secreted in a highly methyl-esterified form and subsequently deesterified in muro by pectin methylesterases (PMEs). In many developmental processes, PMEs are regulated by either differential expression or posttranslational control by protein inhibitors (PMEIs). PMEIs are typically active against plant PMEs and ineffective against microbial enzymes. Here, we describe the three-dimensional structure of the complex between the most abundant PME isoform from tomato fruit (Lycopersicon esculentum) and PMEI from kiwi (Actinidia deliciosa) at 1.9-Å resolution. The enzyme folds into a right-handed parallel b-helical structure typical of pectic enzymes. The inhibitor is almost all helical, with four long a-helices aligned in an antiparallel manner in a classical up-and-down fourhelical bundle. The two proteins form a stoichiometric 1:1 complex in which the inhibitor covers the shallow cleft of the enzyme where the putative active site is located. The four-helix bundle of the inhibitor packs roughly perpendicular to the main axis of the parallel b-helix of PME, and three helices of the bundle interact with the enzyme. The interaction interface displays a polar character, typical of nonobligate complexes formed by soluble proteins. The structure of the complex gives an insight into the specificity of the inhibitor toward plant PMEs and the mechanism of regulation of these enzymes.

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Section: Resultscontrasting

confidence: 99%

Structural Basis for the Interaction between Pectin Methylesterase and a Specific Inhibitor Protein

Matteo¹,

Giovane

Raiola³

et al. 2005

Plant Cell

206

224

View full text Add to dashboard Cite

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“…The conserved tyrosine in motif I may play a role in the catalytic mechanism. Motif II corresponds to the best conserved region, an octapeptide located in the central part of these enzymes (Markovic and Jornvall, 1992).These properties are consistent with the hypothesis that the cDNA encodes a root cap-expressed PME, which we therefore have designated rcpme1 (GenBank accession number AF056493). The deduced amino acid sequence of a partial cDNA, PsPE1 , representing the 3 Ј half of rcpme1 , exhibits 80% homology with the deduced amino acid sequence of the conserved 3 Ј half of genes encoding PMEs from tomato and other organisms (Figure 2A).…”

supporting

confidence: 80%

Section: An Inducible Root Cap Cdna Clone Has Features Common To Pme mentioning

confidence: 99%

Effect of Pectin Methylesterase Gene Expression on Pea Root Development

1999

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Expression of an inducible gene with sequences common to genes encoding pectin methylesterase (PME) was found to be tightly correlated, both spatially and temporally, with border cell separation in pea root caps. Partial inhibition of the gene's expression by antisense mRNA in transgenic pea hairy roots prevented the normal separation of root border cells from the root tip into the external environment. This phenotype was correlated with an increase in extracellular pH, reduced root elongation, and altered cellular morphology. The translation product of the gene exhibited PME activity in vitro. These results are consistent with the long-standing hypothesis that the demethylation of pectin by PME plays a key role in cell wall metabolism. INTRODUCTIONBetween the plant cytoplasm and its external environment lies a complex carbohydrate-based cell wall, which is a dynamic interface that participates directly in cellular responses to exogenous stimuli (reviewed in Albersheim et al., 1994; de Lorenzo et al., 1994). In addition to a direct role in perceiving and responding to incoming signals, the cell wall is a repository of oligosaccharides whose activity can alter the metabolism of the plant cell it encloses as well as that of other organisms that find their way into proximity with the cell. These sugar-based signal molecules are released from cell wall polymers by the action of enzymes that can come from fungi, bacteria, or other organisms in the environment, or from the plant itself. The role of specific plant cell walldegrading enzymes in cell wall metabolism during growth and development remains unclear (reviewed in Carpita et al., 1996).Plant enzymes that degrade pectin, or methylated polygalacturonic acid, are of special interest because this polymer is a major constituent of cell walls and because such pectolytic enzymes can solubilize cell walls (Collmer and Keen, 1986;Koutojansky, 1987). For example, genes encoding certain polygalacturonases (PGs) or pectate lyases (PLs) individually allow soft rot pathogens to macerate potato tuber tissue and to infect plants systemically (Collmer and Keen, 1986). Pectin methylesterase (PME), although it does not by itself solubilize cell walls, has been postulated to regulate cell wall degradation by several mechanisms (e.g., Goldberg et al., 1992). The action of PME reduces pH by the release of a proton when methoxyl groups of pectin are converted to carboxyl groups. This change in pH has been proposed to control the activity of other cell wall-degrading enzymes that are optimally active at low pH and thereby to facilitate cell expansion and growth ) and/or cell separation (Koutojansky, 1987).Demethylation by PME can alter sensitivity of polymers to the action of hydrolases (e.g., Fischer and Bennett, 1991;Liu and Berry, 1991) and expansins (Carpita et al., 1996). Small pectic fragments released by the action of such hydrolases act as signals to induce expression of other pectolytic enzymes, and the degree of methylation of such fragments, dictated by PME activity, ...

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“…In a recent work Recourt et al (1992) showed a 65 to 70% identity between the PME genes isolated from pea pod and the PME genes obtained from fruit cDNA libraries, whereas two fruit PME cDNA clones and three PME genomic clones isolated using a fruit PME cDNA shared more than 90% identity (Ray et al, 1988;Harriman, 1990). The homology recorded between fruit PME genes and pod PME genes could be related to the conservation of active site segments, including the positions of Cys's in tomato, fungal, and bacterial PME genes (Markovic and Jornvall, 1992;Recourt et al, 1992).…”

Section: Discussionmentioning

confidence: 99%

Pectin Methylesterase Isoforms in Tomato (Lycopersicon esculentum) Tissues (Effects of Expression of a Pectin Methylesterase Antisense Gene)

1994

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We have identified two major groups of pectin methylesterase (PME, EC 3.1.1.11) isoforms in various tissues of tomatoes (Lycopersicon esculentum). These two groups exhibited differential immuno-cross-reactivity with polyclonal antibodies raised against tomato fruit PME or flax callus PME and differences in their accumulation patterns in tissues of wild-type and transgenic tomato plants expressing a PME antisense gene. The group I isoforms with isoelectric points (pls) of 8.2, 8.4, and 8.5 are specific to fruit tissue, where they are the major forms of PME activity. The group II PME isoforms, with pl values of 9 and above, are observed in both vegetative and fruit tissues. The group I isoforms cross-react with polyclonal antibodies raised to a PME isoform purified from fruit, whereas the group II isoforms cross-react with antibodies to a PME purified from flax callus. Expression of a fruit-specific PME anti-sense gene impairs accumulation of the group I PME isoforms, with no apparent effect on the accumulation of the group II PME isoforms. The absence of any noticeable effects on growth and development of transgenic plants suggests that the group I PME isoforms are not involved in plant growth and development and may play a role under special circumstances such as cell separation during fruit ripening.

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Disulfide bridges in tomato pectinesterase: Variations from pectinesterases of other species; conservation of possible active site segments

Cited by 35 publications

References 13 publications

Structural Basis for the Interaction between Pectin Methylesterase and a Specific Inhibitor Protein

Structural Basis for the Interaction between Pectin Methylesterase and a Specific Inhibitor Protein

Effect of Pectin Methylesterase Gene Expression on Pea Root Development

Pectin Methylesterase Isoforms in Tomato (Lycopersicon esculentum) Tissues (Effects of Expression of a Pectin Methylesterase Antisense Gene)

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