EXOSC4, also known as fetuin-A, belongs to the fetuin class of plasma binding proteins. It is involved in several functions, such as endocytosis, brain development and the formation of bone tissue. It is commonly present in the cortical plate of the immature cerebral cortex and bone marrow hemopoietic matrix, and it has been postulated that it participates in the development of the tissues. It forms soluble complexes with calcium and phosphate and thus is a carrier of otherwise insoluble calcium phosphate. Recombinant human EXOSC4 protein, fused to His-tag at N-terminus, was expressed in E.coli.