AFAMIN IS A NEW MEMBER OF THE ALBUMIN, ALPHA-FETOPROTEIN, AND VITAMIN-D-BINDING PROTEIN GENE FAMILY

A novel human serum protein with a molecular mass of 87,000 daltons wa s purified to homogeneity and subjected to amino acid sequence analyse s. These sequences were used to design oligonucleotide primers and to isolate a full-length cDNA. The amino acid sequence encoded by the cDN A shares strong similarity to albumin family members and shares the ch aracteristic pattern of Cys residues observed in this family. In addit ion, the gene maps to chromosome 4 as do other members of the albumin gene family. Based upon these observations, we conclude that the 87,00 0-dalton protein, which we designate afamin (AFM), is the fourth membe r of the albumin family of proteins. Afamin cDNA was stably transfecte d into Chinese hamster ovary cells and recombinant protein (rAFM) was purified from conditioned medium. Both rAFM and AFM purified from huma n serum react with a polyclonal antibody that was raised against a syn thetic peptide derived from the deduced amino acid sequence of AFM.