Hemocyanin conformational changes associated with SDS-induced phenol oxidase activation

The enzymatic activity of phenoloxidase is assayed routinely in the presence of SDS. Similar assay conditions elicit phenoloxidase activity in another type 3 copper protein, namely hemocyanin, which normally functions as an oxygen carrier. The nature of the conformational changes induced in type 3 c...

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Bibliographic Details
Published in:Biochimica et biophysica acta 2007-11, Vol.1774 (11), p.1380-1394
Main Authors: Baird, Sharon, Kelly, Sharon M., Price, Nicholas C., Jaenicke, Elmar, Meesters, Christian, Nillius, Dorothea, Decker, Heinz, Nairn, Jacqueline
Format: Article
Language:English
Subjects:
Animals
Catalytic Domain
Copper - metabolism
Enzyme Activation
Hemocyanin
Hemocyanins - chemistry
Hemocyanins - metabolism
Horseshoe Crabs
Isothermal titration calorimetry
Monophenol Monooxygenase - metabolism
Phenoloxidase
Protein Structure, Secondary
Protein Structure, Tertiary
Scorpions
Sodium Dodecyl Sulfate
Spectroscopy
Spiders
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Summary:The enzymatic activity of phenoloxidase is assayed routinely in the presence of SDS. Similar assay conditions elicit phenoloxidase activity in another type 3 copper protein, namely hemocyanin, which normally functions as an oxygen carrier. The nature of the conformational changes induced in type 3 copper proteins by the denaturant SDS is unknown. This comparative study demonstrates that arthropod hemocyanins can be converted from being an oxygen carrier to a form which exhibits phenoloxidase activity by incubation with SDS, with accompanying changes in secondary and tertiary structure. Structural characterisation, using various biophysical methods, suggests that the micellar form of SDS is required to induce optimal conformational transitions in the protein which may result in opening a channel to the di-copper centre allowing bulky phenolic substrates access to the catalytic site.
ISSN:1570-9639
0006-3002
1878-1454
DOI:10.1016/j.bbapap.2007.08.019