Implication of C-Terminal Deletion on the Structure
and Stability of Bovine β-casein |
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Authors: | Phoebe X Qi Edward D Wickham Edwin G Piotrowski Clifton K Fagerquist Harold M Farrell Jr |
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Institution: | (1) U. S. Department of Agriculture, Eastern Regional Research Center, Agricultural Research Service, 600 East Mermaid Lane, Wyndmoor, PA 19038, USA;(2) U. S. Department of Agriculture, Western Regional Research Center, Agricultural Research Service, 800 Buchanan Street, Albany, CA 94710, USA |
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Abstract: | Bovine β-casein (β-CN) with its C-terminal truncated by chymosin digestion, β-CN-(f1-192), was examined and characterized using circular dichroism (CD) under various temperature conditions. CONTIN/LL analysis
of the CD data revealed significant secondary structure disruption in β-CN-(f1-192) relative to its parent protein,β-CN, in the temperature range (5° to 70°C) studied. Near-UV CD spectra indicated significant
temperature dependent structural changes. Analytical ultracentrifugation results showed significant reduction but not complete
abolishment of self-association in β-CN-(f1-192) compared to whole β-casein at 2°–37°C. Furthermore, binding experiments with the common hydrophobic probe – 8-anilino-1-
naphthalene sulfonic acid (ANS) illustrated that β-CN-(f1-192) is nearly incapable of binding to ANS relative to whole β-CN, suggesting a nearly complete open overall tertiary structure
brought about by the C-terminal truncation. It has been demonstrated clearly that the tail peptide β-CN-(f193-209) is important in maintaining the hydrophobic core of β-CN but the residual association observed argues for a minor
role for other sites as well. |
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Keywords: | β -casein C-terminal deletion chymosin cleavage circular dichroism protein structure self-association protein stability conformational transition analytical ultracentrifugation |
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