Related Experiment Video
Updated: Aug 11, 2026
08:43
OLIgo Mass Profiling (OLIMP) of Extracellular Polysaccharides
Published on: June 20, 2010
Polygalacturonase-inhibiting proteins can function as activators of polygalacturonase
G Kemp1, L Stanton, C W Bergmann
1Complex Carbohydrate Research Center and Department of Biochemistry and Molecular Biology, University of Georgia, 315 Riverbend Road, Athens, Georgia 30602-4712, USA.
Molecular Plant-Microbe Interactions : MPMI
|August 13, 2004
Summary
Plant polygalacturonase-inhibiting proteins (PGIPs) typically inhibit fungal endopolygalacturonases (EPGs). However, this study reveals that PGIP-2 can activate certain EPGs, suggesting a broader role beyond inhibition.
Area of Science:
- Plant Pathology
- Biochemistry
- Enzymology
Background:
- Fungal endopolygalacturonases (EPGs) interact with plant polygalacturonase-inhibiting proteins (PGIPs).
- This interaction typically leads to high-affinity inhibition of EPGs, reducing their catalytic rate.
- EPG/PGIP interactions are implicated in plant pathogenesis and the production of oligosaccharin signals.
Purpose of the Study:
- To analyze the interaction products of Phaseolus vulgaris PGIP-2 with five Aspergillus niger EPGs (PGI, PGII, PGA, PGB, PGC).
- To investigate the pH-dependent effects of PGIP-2 on EPG activity, particularly for PGA and PGC.
- To re-evaluate the established role of PGIPs based on observed activation phenomena.
Main Methods:
- Characterization of interaction products between purified PGIP-2 and purified EPGs from Aspergillus niger.
- Enzymatic assays using homogalacturonan as a substrate in the presence of EPGs and PGIP-2.
- pH-dependent analysis of EPG activity modulation by PGIP-2.
Main Results:
- The interaction between PGIP-2 and Aspergillus niger EPGs (PGA and PGC) resulted in either inhibition or activation of EPG activity.
- The observed modulation of EPG activity by PGIP-2 was dependent on the pH of the reaction.
- This contrasts with the typical high-affinity inhibition previously described for EPG/PGIP interactions.
Conclusions:
- The conventional description of PGIPs solely as inhibitors may be incomplete.
- PGIPs, like PGIP-2, can modulate EPG activity, potentially leading to activation under specific conditions.
- The term "polygalacturonase-modulating protein" may better describe the multifaceted role of PGIPs.
More Related Videos
Related Concept Videos
01:52Eukaryotic Transcription Inhibitors
Certain biochemical processes, such as embryonic development and cell growth regulation, depend on the repression of specific genes. DNA binding proteins known as eukaryotic transcription inhibitors regulate the repression of gene expression in eukaryotes. The presence of these inhibitors at the required location and time in the cell is triggered by the presence of hormones and additional signals from other cells.
Eukaryotic transcription inhibitors usually contain two distinct domains, a DNA...
Eukaryotic transcription inhibitors usually contain two distinct domains, a DNA...
01:05Proteoglycans
Glycans, a class of complex heterogeneous molecules, can be covalently attached to proteins to form glycosylated proteins that regulate various physiological and pathological processes. Glycosylated proteins or glycoproteins comprise N-linked and O-linked oligosaccharides. O-glycosylation is the most common type of protein glycosylation. Here, glycans attach to the oxygen atom of the hydroxyl groups of Serine or Threonine residues. O-linked glycosylation occurs later in protein processing,...
01:22Activation and Inactivation of G Proteins
Heterotrimeric G proteins are guanine nucleotide-binding proteins. As the name suggests, heterotrimeric G proteins are composed of three subunits: alpha, beta, and gamma. They remain GDP-bound or GTP-bound inside the cells and switch between inactive/active states. The Gα subunit possesses the nucleotide-binding pocket that binds guanine nucleotides and switches between GDP or GTP-bound states. In contrast, the Gꞵ and Gγ subunits are always bound together with high affinity and are together...
01:09GPCRs Regulate Adenylyl Cylase Activity
Some GPCRs transmit signals through adenylyl cyclase (AC), a transmembrane enzyme. AC helps synthesize second messenger cyclic adenosine monophosphate (cAMP). AC catalyzes cyclization reaction and converts ATP to cAMP by releasing a pyrophosphate. The pyrophosphate is further hydrolyzed to phosphate by the enzyme pyrophosphatase, which drives cAMP synthesis to completion. However, cAMP is rapidly degraded to 5′ AMP by the enzymes phosphodiesterase (PDE), preventing overstimulation of cells.
Two...
Two...
01:26Biosynthesis of Polysaccharides
Polysaccharides such as glycogen and starch are synthesized from nucleoside diphosphate sugars, primarily uridine diphosphate glucose (UDPG) and adenosine diphosphate glucose (ADPG). These activated glucose donors act as key intermediates in carbohydrate metabolism and biosynthesis. UDPG primarily involves glycogen synthesis in animals and many bacteria, while ADPG plays a fundamental role in starch synthesis in plants and certain bacteria.UDPG is formed when glucose-1-phosphate reacts with...
01:23Inhibitors of Gram-positive Cell Wall Synthesis
Bacterial cell walls are typically rigid structures composed mainly of peptidoglycan, a mesh-like polymer that provides mechanical strength and maintains cell shape. The synthesis of peptidoglycan is a crucial process in bacterial growth and serves as a primary target for many antibiotics.Mechanism of Action of Beta-Lactam AntibioticsBeta-lactam antibiotics, such as penicillin, inhibit peptidoglycan synthesis in actively growing cells. These antibiotics share a characteristic four-membered...