Casein, the milk protein is
Phosphoproteins: These contain phosphorus. Casein of milk and vitellin of egg yolk are examples. The phosphoric acid is esterified to the hydroxyl groups of serine and threonine residues of proteins.
Reference: Vasudevan 7th  ed, pg 43
Nucleoprotein
Chromoprotein
Phosphoprotein
Glycoprotein