The formation of casein micelles reconstituted with Ca+2 and added inorganic phosphate is influenced by the non-phosphorylated form of human beta-casein

• Published in: The protein journal Vol. 24; no. 4; pp. 227 - 232
• Main Authors: Sood, Satish M, Erickson, Grant, Slattery, Charles W
• Format: Journal Article
• Language: English
• Published: Netherlands 01.05.2005
• Subjects: Animals; Calcium - chemistry; Calcium Phosphates - chemistry; Caseins - chemistry; Cattle; Humans; Micelles; Milk, Human - chemistry; Nephelometry and Turbidimetry; Phosphates - chemistry; Temperature
• ISSN: 1572-3887; 1875-8355
• DOI: 10.1007/s10930-005-6715-2

The beta-casein (CN) human milk fraction is comprised of a single protein phosphorylated at levels from 0 to 5. Component interactions are dependent on the phosphorylation level. Here, 3 mg/ml of beta-CN-0P, beta-CN-2P, beta-CN-4P, a 2P/4P 1:1 (wt:wt) mixture, or a mixture of all six forms in the ratio in human milk, were mixed with bovine kappa-CN at a kappa/beta molar ratio of 0.33. Measurements were with 0, 5 and 10 mM Ca+2 and 4 and 8 mM added inorganic phosphate (Pi). The turbidity (OD400 nm) and a lack of precipitation as T increased from 4 to 37 degrees C was an index of micelle formation. The results indicate: (1) while micelles will form with Ca+2 alone, added Pi has a significant enhancing effect on micelle formation; (2) the patterns of micelle formation as a function of T are influenced by the beta-CN-0P and beta-CN-1P forms of beta-CN to an unexpected extent.