Zeus, Aesculapius, Amalthea and the proteome of goat milk

The goat whey proteome has been explored in depth via capture with combinatorial peptide ligand libraries (CPLLs) at three different pH values. A total of 452 unique species have been tabulated, a proteome discovery so far unmatched in any single other investigation of milk from any mammalian species. This massive discovery is probably related to: i) the extraordinary load of proteins onto the CPLL beads (i.e. 2 g for each different pH captures) vs. barely 100 μL of beads; ii) the high resolution/high mass accuracy of mass spectral data; and iii) the use of two complementary tools, Mascot and PEAKS, each one contributing to a set of unique protein IDs. Due to the relative paucity of available protein annotations for goat, only 10% of the identified proteins belong to the capra, whereas 52% are specific of sheep and 37% are homologous to that of bovine milk. This work reports the largest description so far of the goat milk proteome, which has been compared with cow's milk proteome and would thus help to understand the importance of low-abundance proteins with respect to the unique biological properties of this nutrient.