Changes in Conformation and Subunit Assembly of Cod Myosin at Low and High pH and after Subsequent Refolding

• Published in: Journal of agricultural and food chemistry Vol. 51; no. 24; pp. 7187 - 7196
• Main Authors: Kristinsson, Hordur G, Hultin, Herbert O
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 19.11.2003
• Subjects: adenosinetriphosphatase; Animals; Biological and medical sciences; cod (fish); enzyme activity; Fish and seafood industries; Fishes; Food industries; Fundamental and applied biological sciences. Psychology; Gadus morhua; Hydrogen-Ion Concentration; molecular conformation; Muscle, Skeletal - chemistry; myosin; Myosins - chemistry; Protein Conformation; Protein Folding; protein secondary structure; protein subunits; Spectrometry, Fluorescence; Static Electricity; Use and upgrading of agricultural and food by-products. Biotechnology; Viscosity; Cod myosin; Refolding; unfolding; Subunit; Fish by product; Molecular assembly; Upgrading; Food industry; Myosin; Animal protein; pH; Cod; alkaline pH; molten globule; acid pH; conformational changes; Conformation
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf026193m

Conformational and structural changes of cod myosin at pH 2.5 and 11 and after subsequent pH readjustment to pH 7.5 were studied. Results suggest that on acid unfolding, the myosin rod may fully dissociate due to electrostatic repulsion within the coiled coil, while it does not dissociate at alkaline pH. Both pHs led to significant conformational changes in the globular head fraction of the myosin heavy chains, suggesting that it takes on a molten globular configuration. A large part of the myosin light chains are lost on both pH treatments. On pH readjustment to neutrality, the heavy chains take on a structural form similar to the native state with the coiled-coil rod reassociating from acid pH while leaving the globular head less packed, more hydrophobic and structurally less stable. The irreversible change brought about in the globular head region leads to the failure of light chains to reassemble onto it, a drastic loss in ATPase activity, and more exposure of reactive thiol groups. The acid and alkali processes therefore lead to substantial changes in the globular part of the myosin molecule and perhaps more importantly to different molecular changes in myosin, depending on which pH treatment is employed. Keywords: Cod myosin; acid pH; alkaline pH; conformational changes; molten globule; unfolding; refolding