Unstructured recombinant polymers and compositions comprising same

1. A fusion protein comprising at least one unstructured recombinant polypeptide (URP) and a heterologous protein, wherein the heterologous protein is a pharmaceutically active protein selected from the group consisting of cytokines, growth factors, enzymes, receptors, microproteins, hormones, toxins, and hirudin, wherein the fusion protein exhibits an increased serum half-life as compared to the heterologous protein lacking said URP, and wherein the at least one URP is characterized in that:

(a) it comprises at least 40 contiguous amino acids;

(b) the sum of glycine (G), aspartate (D), alanine (A), serine (S), threonine (T), glutamate (E) and proline (P) residues contained in the URP constitutes more than 80% of the total amino acids of the URP, and the remainder, when present, consists of Arginine or Lysine, and the remainder does not contain methionine, cysteine, asparagine, and glutamine;

(c) the URP comprises at least three different types of amino acids selected from the group consisting of glycine (G), aspartate (D), alanine (A), serine (S), threonine (T), glutamate (E) and proline (P), wherein one of said at least three different types is glycine (G) or glutamine (E);

(d) at least 50% of the at least 40 contiguous amino acids in said at least one URP sequence are devoid of secondary structure as determined by Chou-Fasman algorithm; and

(e) the URP has a Tepitope score less than −5.

2. The fusion protein of claim 1 , wherein the at least one URP is fused into the heterologous protein at an N-terminus, a C-terminus, into a loop of the heterologous protein, or between domains of the heterologous protein, or into both the N-terminus and the C-terminus of the heterologous protein.

3. The fusion protein of claim 1 , wherein the at least one URP is fused into a loop of the heterologous protein or between domains of the heterologous protein.

4. The fusion protein of claim 1 , exhibiting at least a 2-fold increase in apparent molecular weight as compared to the heterologous protein lacking the at least one URP, wherein the apparent molecular weight is approximated by size exclusion chromatography.

5. The fusion protein of claim 1 , wherein the fusion protein exhibits a serum secretion half-life that is at least four-fold longer as compared to the heterologous protein lacking said at least one URP.

6. The fusion protein of claim 1 , wherein one of the amino acids selected from the group consisting of glycine (G), aspartate (D), alanine (A), serine (S), threonine (T), glutamate (E) and proline (P) alone constitutes more than 20% of the total amino acids said at least one URP.

7. The fusion protein of claim 1 , wherein one of the amino acids selected from the group consisting of glycine (G), aspartate (D), alanine (A), serine (S), threonine (T), glutamate (E) and proline (P) alone constitutes more than 30% of the total amino acids of said at least one URP.

8. The fusion protein of claim 1 , wherein any one type of amino acid is no more than 30% of the total amino acids of the URP.

9. The fusion protein of claim 1 , wherein the at least one URP comprises at least five types of amino acids selected from the group consisting of glycine (G), aspartate (D), alanine (A), serine (S), threonine (T), glutamate (E) and proline (P).

10. The fusion protein of claim 1 , wherein the at least one URP comprises at least six types of amino acids selected from the group consisting of glycine (G), aspartate (D), alanine (A), serine (S), threonine (T), glutamate (E) and proline (P).

11. The fusion protein of claim 1 , wherein the heterologous protein is selected from the group consisting of erythopoetin, interferon, human growth hormone, growth hormone releasing hormone, G-CSF, GM-CSM, insulin, hirudin, TNF-receptor, uricase, thrombin, blood clotting enzyme, VEGF, protropin, somatropin, alteplase, interleukin, factor VII, factor VIII, factor X, factor IX, dornase, glucocerebrosidase, follitropin, and glucagon.

12. The fusion protein of claim 11 , wherein the heterologous protein is a human growth hormone.

13. The fusion protein of claim 11 , wherein the heterologous protein is a blood clotting enzyme.

14. The fusion protein of claim 11 , wherein the heterologous protein is factor VII.

15. The fusion protein of claim 11 , wherein the heterologous protein is factor VIII.

16. The fusion protein of claim 11 , wherein the heterologous protein is factor IX.

17. The fusion protein of claim 11 , wherein the heterologous protein is insulin.

18. The fusion protein of claim 1 , wherein the combined length of the at least one URP exceeds 100 amino acids.

19. The fusion protein of claim 1 , wherein the combined length of the at least one URP exceeds 200 amino acids.

20. The fusion protein of claim 1 , wherein the at least one URP comprises more than 100 contiguous amino acids.

21. The fusion protein of claim 1 , wherein the at least one URP comprises more than 200 contiguous amino acids.

22. A method of producing the fusion protein, comprising:

(a) providing a host cell comprising an expression vector comprising a polynucleotide encoding the fusion protein of claim 1 ;

(b) culturing said host cell in a culture medium under conditions effective to effect expression of said fusion protein from said polynucleotide;

(c) adsorbing said fusion protein onto a chromatography substrate under conditions effective to capture said fusion protein onto the chromatography substrate;

(d) eluting said fusion protein under conditions effective to elute said capture fusion protein; and

(e) recovering said fusion protein.

23. The method of claim 22 , wherein the heterologous protein is selected from the group consisting of erythopoetin, interferon, human growth hormone, growth hormone releasing hormone, G-CSF, GM-CSM, insulin, hirudin, TNF-receptor, uricase, thrombin, blood clotting enzyme, VEGF, protropin, somatropin, alteplase, interleukin, factor VII, factor VIII, factor X, factor IX, dornase, glucocerebrosidase, follitropin, and glucagon.

24. The method of claim 22 , wherein the host cell is a eukaryotic cell.

25. The method of claim 22 , wherein the host cell is a prokaryotic cell.

26. The fusion protein of claim 1 , wherein the URP comprises at least four types of amino acids selected from the group consisting of glycine (G), aspartate (D), alanine (A), serine (S), threonine (T), glutamate (E) and proline (P).

27. The fusion protein of claim 1 , wherein glutamate constitutes at least 5% of the total amino acids of the URP.