Correlation of refined models for casein submicelles with electron microscopic studies of casein

Abstract

To enhance understanding of the milk protein system, an energy minimized three-dimensional (3-D) model of a putative casein submicelle has been constructed using monomeric, χ-, αs1- and β-casein 3-D models. Docking of one χ- and four αs1-casein molecules produced a framework structure whose external portion is composed of the hydrophilic domains of αs1- and χ- and whose central portion contains two large hydrophobic cavities. Preformed symmetric and asymmetric dimers (formed by docking the hydrophobic C terminal regions of two β-casein molecular models) could easily be placed into the two central cavities on the χ-, αs1-framework yielding two plausible energy minimized 3-D structures for submicellar casein. To test these two 3-D structures, theoretical computer generated topographical models were compared to experimental electron microscopic data. Good comparisons of the shapes of the 3-D models with those of the images generated by electron microscopy were achieved for both the symmetric and asymmetric submicelle models. ©1996 Academic Press Limited.