The Protein Journal

, Volume 25, Issue 5, pp 352–360

Reconstituted Micelle Formation Using Reduced, Carboxymethylated Bovine κ-Casein and Human β-Casein

  • Satish M. Sood
  • Tim Lekic
  • Harbir Jhawar
  • Harold M. FarrellJr.
  • Charles W. Slattery
Article

DOI: 10.1007/s10930-006-9022-7

Cite this article as:
Sood, S.M., Lekic, T., Jhawar, H. et al. Protein J (2006) 25: 352. doi:10.1007/s10930-006-9022-7

Abstract

In milk, κ-casein, a mixture of disulfide-bonded polymers, stabilizes and regulates the size of the unique colloidal complex of protein, Ca2+ and inorganic phosphate (Pi) termed the casein (CN) micelle. However, reduced, carboxymethylated bovine κ-CN (RCM-κ) forms fibrils at 37°C and its micelle-forming ability is in question. Here, the doubly- and quadruply-phosphorylated human β-CN forms and 1:1 (wt:wt) mixtures were combined with RCM-κ at different β/κ weight ratios. Turbidity (OD400 nm) and a lack of precipitation up to 37°C were used as an index of micelle formation. Studies were with 0, 5 and 10 mM Ca2+ and 4 and 8 mM Pi. The RCM-κ does form concentration-dependent micelles. Also, β-CN phosphorylation level influences micelle formation. Complexes were low-temperature reversible and RCM-κ fibrils were seen. There appears to be equilibrium between fibrillar and soluble forms since the solution still stabilized after fibril removal. The RCM-κ stabilized better than native bovine κ-CN.

Keywords

Amyloid fibrils colloidal calcium phosphate human β-caseins reconstituted milk micelle formation reduced, carboxymethylated κ-casein 

Abbreviations

CN

casein

β-CN-0P to β-CN-5P

phosphorylation level ranging from 0 to 5, as indicated by number preceding P; Pi, inorganic orthophosphate, RCM-κ, reduced, carboxymethylated bovine κ-CN

N-κ

native bovine κ-CN

Copyright information

© Springer Science+Business Media, Inc. 2006

Authors and Affiliations

  • Satish M. Sood
    • 1
  • Tim Lekic
    • 1
  • Harbir Jhawar
    • 1
  • Harold M. FarrellJr.
    • 2
  • Charles W. Slattery
    • 1
  1. 1.Department of Biochemistry and Microbiology, Biochemistry Division School of Medicine,Loma Linda UniversityLoma LindaUSA
  2. 2.USDA, ARS, Eastern Regional Research CenterWyndmoorUSA