Disclosed is a fusion protein having improved bioactivity comprising a first polypeptide fusion partner and a second polypeptide fusion partner wherein the first fusion partner is linked to the second fusion partner by a mucin-domain polypeptide linker and wherein the bioactivity of the fusion protein is improved as compared to fusion of the first polypeptide fusion partner and the second polypeptide fusion partner in the absence of the mucin-domain polypeptide linker wherein the improved bioactivity of the fusion protein is increased half-life, wherein the first fusion partner is: sTNFR2, CTLA4, TACI, LFA, IL-1RI, IL-1RAcP, VEGF receptor, TPO receptor agonists, EPO receptor agonists, GLP-1, or exendin-4 and wherein the second polypeptide fusion partner comprises all or a portion of an immunoglobulin comprising an Fc region of IgG, IgA, IgE, IgM or IgD.
