Interactions of beta-lactoglobulin variants with kappa-casein and DTNB: formation of a covalent complex
1997
Thresher, W.C. (New Zealand Dairy Research Inst., Palmerston North (New Zealand). Food Science Section)
The rate of reaction of genetic variants of beta-lactoglobulin (beta-Lg) with chemically activated kappa-casein (kappa-Cn) or with 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB/ Ellman's reagent) varied greatly (A more than B more than C). The reactive thiol group of beta-lactoglobulin became accessible to activated kappa-Cn and DTNB at about 60 degrees C which is about 10-15 degrees less than the thermal unfolding temperature of beta-lactoglobulin. All three beta-Lg variants formed mixed disulfides with kappa-Cn and DTNB. The beta-Lg-DTNB complexes were slowly reduced by mercaptoethanol at room temperature. Hence, it appears that the beta-Lg molecule has the ability to refold around a covalently attached ligand and retard further reaction.
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