Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/20/2003
Publication Date: 6/25/2003
Citation: Qi, P.X., Farrell Jr, H.M., Wickham, E.D. 2003. The role of c-terminal region of bovine b-casein. (abstract). The 94th American Oil Chemists Soc. Annual Meeting & Expo. p.54.
Technical Abstract: The effect of C-terminal deletion by chymosin digestion of B-casein, 1-192 fragment (f1-192) on the structure and stability of the parent protein (B-casein) was examined and characterized using circular dichroism (CD) under various solvent conditions. Analytical ultracentrifugation results indicated negligible degree of self-association in f1-192 compared to whole B-casein in the temperature range of 2 degrees - 37 degrees C. CONTIN analysis of the CD data revealed little change in the overall secondary structural content in f1-192 relative to whole B-casein; i.e., 5-10% a-helix, 31-35% turns, and 25-29% extended sheet from 5 to 70 degrees C. The temperature dependence of the CD spectra of f1-192 showed two distinctive conformational transitions at 12 degrees and 34-36 degrees C, whereas four were found in the parent protein at 10 degrees, 33 degrees, 40 degrees C and 78 degrees C. The transition at 12 degrees C may actually represent a general conformational change or cold denaturation in much similar fashion as the 10 degrees C transition in the native protein. The transition at 34-36 degrees C is more likely the reflection of hydrophobic changes in the core of f1-192. Results obtained in this work suggest possible secondary structural disruption of B-casein upon its C-terminal deletion. Moreover, it has been demonstrated conclusively that the C-terminal tail peptide (f193-209) is essential for self-association and formation of a complex with 8-anilino-1-naphthalene sulfonic acid (ANS), a common hydrophobic binding probe. These results may provide further insights on the critical role of the C-terminal region in the natural cellular function of B-casein.