Novel molecular insights into the anti‐oxidative stress response and structure–function of a salt‐inducible cyanobacterial Mn‐catalase

KatB, a salt‐inducible Mn‐catalase, protects the cyanobacterium Anabaena from salinity/oxidative stress. In this report, we provide distinctive insights into the biological–biochemical function of KatB at the molecular level. Anabaena overexpressing the wild‐type KatB protein (KatBWT) detoxified H2O...

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Bibliographic Details
Published in:Plant, cell and environment cell and environment, 2019-08, Vol.42 (8), p.2508-2521
Main Authors: Chakravarty, Dhiman, Bihani, Subhash C., Banerjee, Manisha, Ballal, Anand
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Amino acids
Anabaena
Anabaena - genetics
Anabaena - metabolism
Anabaena - physiology
Bacterial Proteins - chemistry
Bacterial Proteins - physiology
Catalase
Catalase - chemistry
Catalase - physiology
Crystallography
Denaturation
Environmental stress
Hydrogen peroxide
Hydrogen Peroxide - metabolism
Hydrophobicity
KatB protein
Models, Molecular
nonactive site residues
non‐haem peroxidase
Organic chemistry
Oxidative Stress
Protein engineering
Proteins
Proteolysis
Reactive oxygen species
Residues
salinity
Structure-function relationships
Thermal resistance
Xray crystallography
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Summary:KatB, a salt‐inducible Mn‐catalase, protects the cyanobacterium Anabaena from salinity/oxidative stress. In this report, we provide distinctive insights into the biological–biochemical function of KatB at the molecular level. Anabaena overexpressing the wild‐type KatB protein (KatBWT) detoxified H2O2 efficiently, showing reduced burden of reactive oxygen species compared with the strain overproducing KatBF2V (wherein F‐2 is replaced by V). Correspondingly, the KatBWT protein also displayed several folds more activity than KatBF2V. Interestingly, the KatB variants with large hydrophobic amino acids (F/W/Y) were more compact, showed enhanced activity, and were resistant to thermal/chemical denaturation than variants with smaller residues (G/A/V) at the second position. X‐ray crystallography‐based analysis showed that F‐2 was required for appropriate interactions between two subunits. These contacts provided stability to the hexamer, making it more compact. F‐2, through its interaction with F‐66 and W‐43, formed the proper hydrophobic pocket that held the active site together. Consequently, only residues that supported activity (i.e., F/Y/W) were selected at the second position in Mn‐catalases during evolution. This study (a) demonstrates that modification of nonactive site residues can alter the response of catalases to environmental stress and (b) has expanded the scope of amino acids that can be targeted for rational protein engineering in plants. Uniquely, the physiological response of a cyanobacterial Mn‐catalase (KatB) to H2O2 stress is determined by the protein's N‐terminus. A single residue at this end maintains KatB's overall structure/active site, providing new fundamental mechanistic insights into the function of these vital enzymes.
ISSN:0140-7791
1365-3040
DOI:10.1111/pce.13563