Disclosed is a fusion protein comprising a mucin-domain polypeptide linked to at least one active protein wherein the mucin-domain polypeptide has at least 4 tandem amino acid repeating units of at least 8 amino acids in length per tandem repeating unit, wherein the active protein is selected from: IL-1Ra and exendin-4 and wherein the half-life of the fusion protein is increased by at least two fold as compared to the half-life of the corresponding active protein that is not fused to the mucin-domain polypeptide.
