Abstract
Sedimentation equilibrium experiments of folate-binding protein from cow's milk performed in the analytical ultracentrifuge at pH 5.0 showed a single molecular species with a molecular weight of 30,000. In contrast, at pH 7.4 sedimentation equilibrium indicated molecular weights ranging from about 30,000 to at least 300,000. Sedimentation velocity experiments at pH 5.0 showed a single symmetrical peak with s20,w=2.8 S in agreement with a molecular weight of about 30,000. At pH 6.0 was seen a faster moving boundary (s20,w∼6S) in addition to the slow one. At higher pH two peak maxima were seen: a slow one with sedimentation coefficients of about 5S and a fast one increasing from 9S to 11S with increasing pH. Addition of folate further increased the sedimentation rates. By assuming thatGilbert's rapid monomer-n-mer equilibrium theory was valid also for a lower polymer in equilibrium with a higher polymer our data can be interpreted as an equilibrium between a tetramer and a polymer consisting of more than 16 monomers. In the case of folate addition the results may similarly be interpreted as an equilibrium between an octamer and a polymer composed of more than 32 monomers.
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Abbreviations
- FBP:
-
folate-binding protein
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Pedersen, T.G., Svendsen, I., Hansen, S.I. et al. Aggregation of a folate-binding protein from cow's milk. Carlsberg Res. Commun. 45, 161–166 (1980). https://doi.org/10.1007/BF02906517
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DOI: https://doi.org/10.1007/BF02906517