The present invention provides therapeutic agents and compositions comprising elastic peptides and therapeutic proteins. Such peptides exhibit a flexible, extended conformation. In some embodiments, the therapeutic protein is a GLP-1 receptor agonist (e.g., GLP-1, exendin), insulin, or Factor VII/VIIa, including functional analogs. The present invention further provides encoding polynucleotides, as well as methods of making and using the therapeutic agents. The therapeutic agents have improvements in relation to their use as therapeutics, including, inter alia, one or more of half-life, clearance and/or persistance in the body, solubility, and bioavailability.