The nourishment to mammalian infants is provided by

In plants, P-protein is involved in transport of organic compounds through phloem. Many proteins are stored to serve as reservoirs of amino acids and nitrogen. For instance, seeds of many plants store nutrient protein required for germination and growth of seedlings. Similarly, ovalbumin of egg white provides nourishment to developing bird embryo and casein of milk provides nourishment to mammalian infants. Ferritin protein of bacteria and plant and animal cells stores iron.