Abstract
Bovine κ-casein, the stabilizing protein of the colloidal milk protein complex, has a unique disulfide bonding pattern. The protein exhibits varying molecular sizes on SDS-PAGE ranging from monomer to octamer and above in the absence of reducing agents. Heating the samples with SDS prior to electrophoresis caused an apparent decrease in polymeric distribution: up to 60% monomer after 30min at 90°C as estimated by densitometry of SDS-PAGE. In contrast, heating the samples without detergent at 90 or 37°C caused a significant increase in high-molecular-weight polymers as judged by electrophoresis and analytical ultracentrifugation. In 6 M urea, the protein could be completely reduced, but upon dialysis, varying degrees of polymer reformation occurred depending on the dialysis conditions. Spontaneous reoxidation to polymeric forms is favored at low pH (<5.15) and low ionic strength. The results are discussed with respect to the influence of the method of preparation on the polymer size of κ-caseins and on their resultant physical chemical properties.
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Groves, M.L., Wickham, E.D. & Farrell, H.M. Environmental Effects on Disulfide Bonding Patterns of Bovine κ-Casein. J Protein Chem 17, 73–84 (1998). https://doi.org/10.1023/A:1022518613574
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DOI: https://doi.org/10.1023/A:1022518613574