The cyanobacterial hepatotoxin microcystin binds to proteins and increases the fitness of microcystis under oxidative stress conditions

Microcystins are cyanobacterial toxins that represent a serious threat to drinking water and recreational lakes worldwide. Here, we show that microcystin fulfils an important function within cells of its natural producer Microcystis. The microcystin deficient mutant ΔmcyB showed significant changes...

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Bibliographic Details
Published in:PloS one 2011-03, Vol.6 (3), p.e17615
Main Authors: Zilliges, Yvonne, Kehr, Jan-Christoph, Meissner, Sven, Ishida, Keishi, Mikkat, Stefan, Hagemann, Martin, Kaplan, Aaron, Börner, Thomas, Dittmann, Elke
Format: Article
Language:English
Subjects:
Abiotic stress
Anabaena
Binding
Biochemistry
Biology
Biosynthesis
Calvin cycle
Cell division
Cyanobacteria
Cysteine
Cystine
Daphnia
Data processing
Deficient mutant
Drinking water
Environmental conditions
Enzymes
Experiments
Fitness
Genes
Hepatotoxicity
Hydrogen
Hydrogen peroxide
Lakes
Light
Light effects
Metabolites
Microcystins
Microcystins - metabolism
Microcystis
Microcystis - enzymology
Microcystis - metabolism
Microcystis aeruginosa
Microorganisms
Mutagenesis
NADP
Oxidation-Reduction
Oxidative Stress
Peptides
Peroxides
Phycobiliproteins
Planktothrix agardhii
Plant metabolites
Proteases
Protein Binding
Proteinase
Proteins
reductase
Reductases
Ribulose-bisphosphate carboxylase
Ribulose-Bisphosphate Carboxylase - metabolism
Secondary metabolites
Stress response
Studies
Synechocystis
Toxins
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Summary:Microcystins are cyanobacterial toxins that represent a serious threat to drinking water and recreational lakes worldwide. Here, we show that microcystin fulfils an important function within cells of its natural producer Microcystis. The microcystin deficient mutant ΔmcyB showed significant changes in the accumulation of proteins, including several enzymes of the Calvin cycle, phycobiliproteins and two NADPH-dependent reductases. We have discovered that microcystin binds to a number of these proteins in vivo and that the binding is strongly enhanced under high light and oxidative stress conditions. The nature of this binding was studied using extracts of a microcystin-deficient mutant in vitro. The data obtained provided clear evidence for a covalent interaction of the toxin with cysteine residues of proteins. A detailed investigation of one of the binding partners, the large subunit of RubisCO showed a lower susceptibility to proteases in the presence of microcystin in the wild type. Finally, the mutant defective in microcystin production exhibited a clearly increased sensitivity under high light conditions and after hydrogen peroxide treatment. Taken together, our data suggest a protein-modulating role for microcystin within the producing cell, which represents a new addition to the catalogue of functions that have been discussed for microbial secondary metabolites.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0017615