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 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.
Baird
Sharon
S
School of Biological and Environmental Sciences, University of Stirling, Stirling FK9 4LA, Scotland, UK.
Kelly
Sharon M
SM
Price
Nicholas C
NC
Jaenicke
Elmar
E
Meesters
Christian
C
Nillius
Dorothea
D
Decker
Heinz
H
Nairn
Jacqueline
J
D000818:Animals; D020134:Catalytic Domain; D003300:Copper / Q000378:metabolism; D004789:Enzyme Activation; D006433:Hemocyanins / Q000737:chemistry* / Q000378:metabolism*; D006737:Horseshoe Crabs; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012605:Scorpions; D012967:Sodium Dodecyl Sulfate; D013112:Spiders
D012967:Sodium Dodecyl Sulfate; D003300:Copper; D006433:Hemocyanins; D014442:Monophenol Monooxygenase