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Updated: May 27, 2026

A Kinetic Fluorescence-based Ca2+ Mobilization Assay to Identify G Protein-coupled Receptor Agonists, Antagonists, and Allosteric Modulators
Published on: February 20, 2018
Pasteurella multocida toxin activates various heterotrimeric G proteins by deamidation
Joachim H C Orth1, Klaus Aktories
1Institute for Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, 79104 Freiburg, Germany. Joachim.Orth@pharmakol.uni-freiburg.de
Pasteurella multocida toxin (PMT) activates G proteins by preventing GTP hydrolysis, leading to altered cellular signaling. This study details PMT's molecular mechanism and its impact on cell pathways.
Area of Science:
- Microbiology
- Molecular Biology
- Cellular Biology
Background:
- Pasteurella multocida toxin (PMT) is a virulence factor that disrupts host cell signaling.
- PMT targets heterotrimeric G proteins, crucial regulators of cellular processes.
Purpose of the Study:
- To elucidate the molecular mechanism of PMT action.
- To analyze the structure-function relationship of PMT.
- To discuss the impact of PMT on cellular signaling pathways.
Main Methods:
- Crystal structure analysis of PMT.
- Investigation of PMT's molecular mode of action.
- Analysis of cellular signal transduction pathways affected by PMT.
Main Results:
- PMT deamidates a critical glutamine residue in G protein α-subunits, inhibiting GTP hydrolysis and locking them in an active state.
- Substrates include Gα(q), Gα(13), and Gα(i)-family proteins.
- Activated pathways include phospholipase Cβ, Rho-guanine nucleotide exchange factors, and adenylyl cyclase inhibition.
Conclusions:
- PMT employs a unique mechanism to constitutively activate specific G proteins.
- Understanding PMT's action provides insights into bacterial pathogenesis and host-pathogen interactions.
- This knowledge aids in developing strategies to counteract PMT's effects.
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