Coacervates of Lactotransferrin and β- or κ-Casein: Structure Determined Using SAXS

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  • C G Kees de Kruif, Van 't Hoff laboratory for Physical and Colloid Chemistry, Padualaan 8, Utrecht University, The Netherlands. C.G.deKruif@UU.NL, Netherlands
  • Jan Skov Pedersen
  • Thom Huppertz, NIZO food research, Ede, Netherlands
  • Skelte G Anema, Fonterra Research Centre, Palmerston North, New Zealand
Lactotransferrin (LF) is a large globular protein in milk with immune-regulatory and bactericidal properties. At pH 6.5, LF (M = 78 kDa) carries a net (calculated) charge of +21. β-Casein (BCN) and κ-casein (KCN) are part of the casein micelle complex in milk. Both BCN and KCN are amphiphillic proteins with a molar mass of 24 and 19 kDa and carry net charges of -14 and -4, respectively. Both BCN and KCN form soap-like micelles, with 40 and 65 monomers, respectively. The net negative charges are located in the corona of the micelles. On mixing LF with the caseins, coacervates are formed. We analyzed the structure of these coarcervates using SAXS. It was found that LF binds to the corona of the micellar structures, at the charge neutrality point. BCN/LF and KCN/LF ratios at the charge neutrality point were found to be ~1.2 and ~5, respectively. We think that the findings are relevant for the protection mechanism of globular proteins in bodily fluids where unstructured proteins are abundant (saliva). The complexes will prevent docking of enzymes on specific charged groups on the globular protein.
Original languageEnglish
JournalLangmuir
Volume29
Issue33
Pages (from-to)10483-10490
Number of pages8
ISSN0743-7463
DOIs
Publication statusPublished - 2013

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