CORRELATION OF REFINED MODELS FOR CASEIN SUBMICELLES WITH ELECTRON-MICROSCOPIC STUDIES OF CASEIN

To enhance understanding of the milk protein system, an energy minimiz ed three-dimensional (3-D) model of a putative casein submicelle has b een constructed using monomeric, alpha(s1) and beta-casein 3-D models. Docking of one kappa-and four alpha(s1)-casein molecules produced a f ramework structure whose external portion is composed of the hydrophil ic domains of alpha(s1)- and kappa- and whose central portion contains two large hydrophobic cavities. Preformed symmetric and asymmetric di mers (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 en ergy minimized 3-D structures for submicellar casein. To test these tw o 3-D structures, theoretical computer generated topographical models were compared to experimental electron microscopic data. Good comparis ons of the shapes of the 3-D models with those of the images generated by electron microscopy were achieved for both the symmetric and asymm etric submicelle models. (C) 1996 Academic Press Limited