Proteomic characterization of donkey milk "caseome"

Area of Science:

• Biochemistry
• Proteomics
• Dairy Science

Background:

• Donkey milk casein characterization is less advanced than bovine milk.
• Limited data exists on donkey milk casein genetic polymorphism.

Purpose of the Study:

• To investigate the heterogeneity of the donkey milk caseome.
• To identify different casein components and their variations.

Main Methods:

• Proteomic approach utilizing one-dimensional (PAGE, UTLIEF) and two-dimensional (PAGE-->UTLIEF) electrophoresis.
• Staining with Coomassie Brilliant Blue or specific polyclonal antibodies.
• Structural Mass Spectrometry (MS) analysis.

Main Results:

• Identification of donkey alpha(s1), alpha(s2), beta, and kappa-caseins.
• Characterization of heterogeneity due to phosphorylation (alpha(s1), alpha(s2), beta-CN), glycosylation (kappa-CN), and RNA splicing errors (deleted forms).
• Quantification of casein components: 11 kappa-CN, six phosphorylated beta- and alpha(s1)-CN, and three phosphorylated alpha(s2)-CN variants.

Conclusions:

• The study provides a comprehensive characterization of donkey milk casein heterogeneity.
• New insights into genetic polymorphism and post-translational modifications of donkey caseins were revealed.
• The primary structure of donkey alpha(s2)-casein was determined for the first time.