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The dissociated form of kappa-casein is the precursor to its amyloid fibril formation

Journal Article


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Abstract


  • Bovine milk kappa-casein forms a self-associating oligomeric micelle-like species, in equilibrium with dissociated forms. In its native form, intra- and inter-molecular disulfide bonds lead to the formation of multimeric species ranging from monomers to decamers. When incubated under conditions of physiological pH and temperature, both reduced and non-reduced kappa-casein form highly structured beta-sheet amyloid fibrils. We investigated whether the precursor to kappa-casein fibril formation is a dissociated state of the protein or its oligomeric micelle-like form. We show that reduced kappa-casein is capable of forming fibrils well below its critical micelle concentration, i.e. at concentrations where only dissociated forms of the protein are present. Moreover, by regulating the degree of disulfide linkages, we were able to investigate how oligomerization of kappa-casein influences its propensity for fibril formation under conditions of physiological pH and temperature. Thus, using fractions containing different proportions of multimeric species, we demonstrate that the propensity of the disulfide-linked multimers to form fibrils is inversely related to their size, with monomeric kappa-casein being the most aggregation prone. We conclude that dissociated forms of kappa-casein are the amyloidogenic precursors to fibril formation rather than oligomeric micelle-like species. The results highlight the role of oligomerization and natural binding, partners in preventing amyloid fibril formation by disease-related proteins in vivo.

Authors


  •   Ecroyd, Heath
  •   Thorn, David C. (external author)
  •   Liu, Yanqin (external author)
  •   Carver, John A. (external author)

Publication Date


  • 2010

Citation


  • Ecroyd, H., Thorn, D., Liu, Y. & Carver, J. A. (2010). The dissociated form of kappa-casein is the precursor to its amyloid fibril formation. Biochemical Journal, 429 (2), 251-260.

Scopus Eid


  • 2-s2.0-77954710921

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=1462&context=scipapers

Ro Metadata Url


  • http://ro.uow.edu.au/scipapers/424

Has Global Citation Frequency


Number Of Pages


  • 9

Start Page


  • 251

End Page


  • 260

Volume


  • 429

Issue


  • 2

Abstract


  • Bovine milk kappa-casein forms a self-associating oligomeric micelle-like species, in equilibrium with dissociated forms. In its native form, intra- and inter-molecular disulfide bonds lead to the formation of multimeric species ranging from monomers to decamers. When incubated under conditions of physiological pH and temperature, both reduced and non-reduced kappa-casein form highly structured beta-sheet amyloid fibrils. We investigated whether the precursor to kappa-casein fibril formation is a dissociated state of the protein or its oligomeric micelle-like form. We show that reduced kappa-casein is capable of forming fibrils well below its critical micelle concentration, i.e. at concentrations where only dissociated forms of the protein are present. Moreover, by regulating the degree of disulfide linkages, we were able to investigate how oligomerization of kappa-casein influences its propensity for fibril formation under conditions of physiological pH and temperature. Thus, using fractions containing different proportions of multimeric species, we demonstrate that the propensity of the disulfide-linked multimers to form fibrils is inversely related to their size, with monomeric kappa-casein being the most aggregation prone. We conclude that dissociated forms of kappa-casein are the amyloidogenic precursors to fibril formation rather than oligomeric micelle-like species. The results highlight the role of oligomerization and natural binding, partners in preventing amyloid fibril formation by disease-related proteins in vivo.

Authors


  •   Ecroyd, Heath
  •   Thorn, David C. (external author)
  •   Liu, Yanqin (external author)
  •   Carver, John A. (external author)

Publication Date


  • 2010

Citation


  • Ecroyd, H., Thorn, D., Liu, Y. & Carver, J. A. (2010). The dissociated form of kappa-casein is the precursor to its amyloid fibril formation. Biochemical Journal, 429 (2), 251-260.

Scopus Eid


  • 2-s2.0-77954710921

Ro Full-text Url


  • http://ro.uow.edu.au/cgi/viewcontent.cgi?article=1462&context=scipapers

Ro Metadata Url


  • http://ro.uow.edu.au/scipapers/424

Has Global Citation Frequency


Number Of Pages


  • 9

Start Page


  • 251

End Page


  • 260

Volume


  • 429

Issue


  • 2