Minor proteins

Abstract

Egg white is generally presented as an aqueous solution of major and minor proteins. Structure and properties of major proteins are well known, whereas the minor proteins have been little studied, and all are not yet identified. Unfortunately, until recently no highly efficient methods were available to simultaneously analyze all the hen egg white proteins. Indeed, this biological fluid is unique and presents some difficulties for analysis. The proteins have very different molecular weights (12.7 to 8,000 kDa) and pI values (4 to 11; Li-Chan and Nakai 1989). Concentrations of these minor proteins differ greatly, and complicated by the fact, for instance, that ovalbumin represents more than 50% of total proteins, their detection is often very difficult. These reasons probably explain why very little research has been devoted to the identification and characterization of the minor egg white proteins, even though they probably play essential roles with respect to the primary biological action of egg white, i.e., embryo protection and development. So, hen egg white remains surprisingly uncharacterized. The identification of these minor proteins necessitates high-resolution methods for protein separation, and two-dimensional electrophoresis has proved to be particularly efficient. This technique has highlighted the proposition that indeed many unidentified minor proteins are present in hen egg white. (Desert et al. 2001). Some of these minor proteins presented in this section were very recently identified. © Springer-Verlag Berlin Heidelberg 2007.