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G-actin conformational change and polymerization induced by paraquat
I DalleDonne1, A Milzani, R Colombo
1University of Milan, Department of Biology, Italy.
Summary
Paraquat herbicide induces structural changes in actin, a key cytoskeletal protein. This leads to actin oligomerization and ATP hydrolysis, contributing to cellular damage.
Area of Science:
- Biochemistry
- Cell Biology
- Toxicology
Background:
- Paraquat is a toxic herbicide causing lung damage.
- Paraquat alters mammalian cell cytoskeleton organization and protein synthesis.
- Previous work showed paraquat binds actin and forms aggregates.
Purpose of the Study:
- Investigate paraquat's effects on actin structure and function.
- Elucidate the mechanism of paraquat-induced actin alterations.
Main Methods:
- Fluorescence quenching assays to study Trp residues in actin.
- Trypsin digestion to analyze conformational changes.
- Intermolecular cross-linking to characterize actin oligomers.
- ATP hydrolysis assays.
Main Results:
- Paraquat binding quenches actin's Trp-79 and Trp-86 fluorescence.
- Paraquat induces conformational changes in actin subdomain 2 (residues 61-69).
- Paraquat-treated actin partially loses its ability to inhibit DNase I.
- Paraquat promotes G-actin oligomerization with specific subunit contacts.
- Paraquat-induced actin oligomerization is coupled with ATP hydrolysis.
Conclusions:
- Paraquat directly alters actin structure and promotes its oligomerization.
- These paraquat-induced changes in actin may contribute to cellular toxicity.
- The mechanism involves conformational changes, altered protein interactions, and ATP hydrolysis.