title: An energy-minimized casein submicelle working model.
abstract: To develop a molecular basis for structure-function relationships of the complex milk protein system, an energy-minimized, three-dimensional model of a casein submicelle was constructed consisting of kappa-casein, four alpha s1-casein, and four beta-casein molecules. The models for the individual caseins were from previously reported energy-minimized, three-dimensional structures. Docking of one kappa-casein and four alpha s1-casein molecules produced a framework structure through the interaction of two hydrophobic antiparallel sheets of kappa-casein with two small hydrophobic antiparallel sheets (residue 163-174) of two preformed alpha s1-casein dimers. The resulting structure is approximately spherically symmetric, with a loose packing density; its external portion is composed of the hydrophilic domains of the four alpha s1-caseins, while the central portion contains two hydrophbic cavities on either side of the kappa-casein central structure. Symmetric and asymmetric preformed dimers of beta-casein formed from the interactions of C-terminal beta-spiral regions as a hinge point could easily be docked into each of the two central cavities of the alpha-kappa framework. This yielded two plausible energy-minimized, three-dimensional structures for submicellar casein, one with two symmetric beta-casein dimers and one with two asymmetric dimers. These refined submicellar structures are in good agreement with biochemical, chemical, and solution structural information available for submicellar casein.
authors.affiliation: Eastern Regional Research Center, ARS, USDA, Philadelphia, Pennsylvania 19118, USA.
authors.forename: T F
authors.initials: TF
authors.lastname: Kumosinski
authors.forename: G
authors.initials: G
authors.lastname: King
authors.forename: H M
authors.initials: HM
authors.lastname: Farrell
mesh_terms: D000818:Animals; D002364:Caseins / Q000737:chemistry*; D002417:Cattle; D008958:Models, Molecular; D011487:Protein Conformation; D017433:Protein Structure, Secondary
chemical_list: D002364:Caseins