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Title: AN ENERGY-MINIMIZED CASEIN SUBMICELLE WORKING MODEL

Author
item KUMOSINSKI T F - 1935-35-00
item King, Gregory
item FARRELL JR H M - 1935-35-00

Submitted to: Journal of Protein Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/12/1994
Publication Date: N/A
Citation: N/A

Interpretive Summary: The most important sources of calcium in the diets of Americans are milk and dairy products. The calcium of milk is bound in a very unique way with the caseins or milk proteins. Understanding how these complexes form, carry the calcium and are changed by processing conditions is important to insure healthful nutritious products for the future. It is not possible at this time to study these milk calcium-protein complexes directly to unravel their nature. To overcome this problem, we have begun to build molecular models with a computer. In this study a part of milk protein which carries nearly all of the calcium was studied. The effects of changes in the chemistry of milk with processing can be reconciled at the molecular level and thus the food industry can now use these models to improve processing of milk products.

Technical Abstract: To enhance understanding of the milk protein system, an energy minimized three dimensional (3D) model of a putative casein submicelle was constructed using monomeric Kappa-, Alpha S1- and Beta-casein 3D models. Docking of one Kappa- and four Alpha S1-casein molecules produced a framework structure, whose external portion is composed of the hydrophilic domains of Alpha S1- and Kappa- and whose central portion contains two large hydrophobic cavities. Preformed symmetric and asymmetric dimers (formed by docking the hydrophobic C terminal regions of two Beta-casein molecular models) could easily be placed into the two central cavities on the Kappa-, Alpha S1- framework yielding two plausible energy minimized 3D structures for submicellar casein. To test these two refined, 3D structures, theoretical computer generated topographical models were compared to chemical and biochemical data. Good comparisons of the 3D models were found.