Related Experiment Video

Updated: Jul 12, 2026

Double-Staining Method to Detect Pectin in Plant-Fungus Interaction
06:39

Double-Staining Method to Detect Pectin in Plant-Fungus Interaction

Published on: February 4, 2022

Molecular basis of the activity of the phytopathogen pectin methylesterase

Markus Fries1, Jessica Ihrig, Keith Brocklehurst

  • 1School of Biological and Chemical Sciences, Queen Mary, University of London, London, UK.

The EMBO Journal
|August 25, 2007
PubMed

Insights

We elucidated the mechanism of pectin methylesterase (PME), an enzyme crucial for bacterial plant tissue invasion. Structural and kinetic data reveal how PME binds and processes pectin, detailing its essential catalytic residues and processive action.

Area of Science:

  • Biochemistry
  • Enzymology
  • Plant Pathology

Background:

  • Pectin methylesterase (PME) initiates bacterial invasion of plant tissues by modifying pectin.
  • Previous work identified PME as a novel aspartic-esterase with a parallel beta-helix structure.

Purpose of the Study:

  • To elucidate the catalytic mechanism and substrate specificity of Erwinia chrysanthemi PME at atomic resolution.
  • To understand the processive action and sequential demethylation of pectin by PME.

Main Methods:

  • X-ray crystallography of PME-pectin complexes.
  • Kinetic measurements using directed mutants.
  • Analysis of product complexes and enzyme-substrate interactions.

Main Results:

  • Identified two conserved aspartates as the nucleophile and general acid-base catalyst.
  • Revealed essential roles for other catalytic residues in substrate binding and transition state stabilization.
  • Demonstrated preferential binding of methylated pectin upstream and demethylated residues downstream, driving processive action.

Conclusions:

  • The study provides a detailed atomic-level mechanism for PME activity.
  • Pectin binding and demethylation pattern are dictated by specific interactions with methylated and demethylated residues.
  • This mechanism explains the sequential demethylation observed in both bacterial and plant PMEs.

More Related Videos

Genetic Manipulation of the Plant Pathogen Ustilago maydis to Study Fungal Biology and Plant Microbe Interactions11:42

Genetic Manipulation of the Plant Pathogen Ustilago maydis to Study Fungal Biology and Plant Microbe Interactions

Published on: September 30, 2016

In Vitro Assay to Measure Phosphatidylethanolamine Methyltransferase Activity09:33

In Vitro Assay to Measure Phosphatidylethanolamine Methyltransferase Activity

Published on: January 5, 2016

Related Concept Videos

Cellulose and Pectic Polysaccharides01:15

Cellulose and Pectic Polysaccharides

Every plant cell has a cell wall that protects the cell, provides structural support, and gives the cell shape. Cellulose, the main structural component of the plant cell wall, makes up over 30% of plant matter. It is the most abundant organic compound on earth.  Cellulose is an unbranched polysaccharide composed of linear chains of glucose molecules linked by β (1→4) glycosidic bonds.
As a cell matures, its cell wall specializes according to its type. For example, the parenchyma cells of...
Gene Regulation in Microbial Communities: Quorum Sensing01:28

Gene Regulation in Microbial Communities: Quorum Sensing

Quorum sensing is a mechanism of bacterial communication that enables coordinated gene expression in response to changes in population density. This facilitates collective behaviors that enhance survival, resource acquisition, and ecological adaptation. This process relies on small signaling molecules called autoinducers that accumulate as bacterial populations grow. When a critical threshold concentration of autoinducers is reached, bacterial cells collectively modify gene expression,...
Restriction Enzymes01:11

Restriction Enzymes

Restriction enzymes are bacterial enzymes used to cut DNA in a sequence-specific manner. To cleave DNA, they bind to specific palindromic sequences called restriction sites. Such palindromic DNA sequences or inverted repeats are commonly found in regions of functional significance, such as the origin of replication, gene operator sites, and regions containing transcription termination signals.
The host bacteria protect their own genomic DNA from these enzymes by methylating these sites. Some...
Role of Microtubules in Cell Wall Deposition01:02

Role of Microtubules in Cell Wall Deposition

Microtubules are small hollow tubes in eukaryotic cells. The cell wall microtubules are polymerized dimers of two globular proteins, α-tubulin and β-tubulin, two globular proteins. With a diameter of about 25 nm, microtubules are the widest components of the cytoskeleton. They help the cell resist compression and provide a track along which vesicles move through the cell or pull replicated chromosomes to opposite ends of a dividing cell. Microtubules go through quick cycles of disassembly and...