Protein scaffolds

1. A recombinant polypeptide scaffold comprising:

I. seven beta strand domains designated A, B, C, D, E, F, and G, having the amino acids of:

a) SEQ ID NO:239 for the A beta strand, SEQ ID NO:229 for the B beta strand, SEQ ID NO:230 for the C beta strand, SEQ ID NO: 236 for the D beta strand, SEQ ID NO:232 for the E beta strand, SEQ ID NO:245 for the F beta strand and SEQ ID NO:246 for the G beta strand; or

b) SEQ ID NO:239 for the A beta strand, SEQ ID NO:229 for the B beta strand, SEQ ID NO:247 for the C beta strand, SEQ ID NO: 236 for the D beta strand, SEQ ID NO:232 for the E beta strand, SEQ ID NO:248 for the F beta strand, and SEQ ID NO:234 for the G beta strand;

II. linked to six loop regions such that a loop region connects each beta strand domain, is designated AB, BC, CD, DE, EF, and FG and corresponds to the cognate loop regions of SEQ ID NO:1, the cognate loop regions of SEQ ID NO: 1 consisting of residues:

a) from 11 to 17 inclusive in an AB loop;

b) from 23 to 31 inclusive in an BC loop;

c) from 39 to 45 inclusive in an CD loop;

d) from 51 to 56 inclusive in an DE loop;

e) from 23 to 31 inclusive in an EF loop;

f) from 23 to 31 inclusive in an FG loop,

at least one of said loop regions being a non-naturally occurring variant of the cognate loop region in SEQ ID NO: 1; and

III. a disulfide bond linking the F and G beta strand domains or linking the C and F beta strand domains,

wherein said scaffold binds a target.

2. The scaffold of claim 1 , wherein said BC loop is a non-naturally occurring variant and consists of 9 amino acids having a sequence of S-X-a-X-b-X-X-X-G, wherein X represents any amino acid, wherein (a) represents proline or alanine and wherein (b) represents alanine or glycine.

3. The scaffold of claim 1 , wherein said BC loop is a non-naturally occurring variant and consists of 11 amino acids having a sequence of S-P-c-X-X-X-X-X-X-T-G (SEQ ID NO: 258), wherein X represents any amino acid and wherein (c) represents proline, serine or glycine.

4. The scaffold of claim 1 , wherein said BC loop is a non-naturally occurring variant and consists of 12 amino acids having a sequence of A-d-P-X-X-X-e-f-X-I-X-G (SEQ ID NO: 257), wherein X represents any amino acid, wherein (d) represents proline, glutamate or lysine, wherein (e) represents asparagine or glycine, and wherein (f) represents serine or glycine.

5. The scaffold of claim 1 , wherein said FG loop is a non-naturally occurring variant and consists of 9 amino acids having a sequence of X-a-X-X-G-X-X-X-S, wherein X represents any amino acid and wherein (a) represents asparagine, threonine or lysine.

6. The scaffold of claim 1 , wherein said FG loop is a non-naturally occurring variant and consists of 10 amino acids having a sequence of X-a-X-X-X-X-b-N-P-A, wherein X represents any amino acid, wherein (a) represents asparagine, threonine or lysine and wherein (b) represents serine or glycine.

7. The scaffold of claim 1 , wherein said FG loop is a non-naturally occurring variant and consists of 11 amino acids having a sequence of X-a-X-X-G-X-X-S-N-P-A (SEQ ID NO: 259), wherein X represents any amino acid, and wherein (a) represents asparagine, threonine or lysine.

8. The scaffold of claim 1 , wherein said DE loop is a non-naturally occurring variant and consists of 6 amino acids having a sequence of X-X-X-X-X-X, wherein X represents any amino acid.

9. The scaffold of claim 1 , wherein said AB loop is a non-naturally occurring variant and consists of 7 residues having the sequence: K-X-X-X-X-X-a, wherein X represents asparagine, aspartic acid, histidine, tyrosine, isoleucine, valine, leucine, phenylalanine, threonine, alanine, proline, or serine, and wherein (a) represents serine, threonine, alanine, or glycine.

10. The scaffold of claim 1 , wherein said AB loop is a non-naturally occurring variant and consists of 9 residues having the sequence: K-X-X-X-X-X-X-X-a, wherein X represents asparagine, aspartic acid, histidine, tyrosine, isoleucine, valine, leucine, phenylalanine, threonine, alanine, proline, or serine, and wherein (a) represents serine, threonine, alanine, or glycine.

11. The scaffold of claim 1 , wherein said CD loop is a non-naturally occurring variant and consists of 7, 8, or 9 residues wherein each residue in the CD loop is randomized and wherein each residue may be asparagine, aspartic acid, histidine, tyrosine, isoleucine, valine, leucine, phenylalanine, threonine, alanine, proline, or serine.

12. The scaffold of claim 1 , wherein said EF loop is a non-naturally occurring variant and consists of 8 residues having the sequence X-b-L-X-P-X-c-X, wherein X represents asparagine, aspartic acid, histidine, tyrosine, isoleucine, valine, leucine, phenylalanine, threonine, alanine, proline, or serine, wherein (b) represents asparagine, lysine, arginine, aspartic acid, glutamic acid, or glycine, and wherein (c) represents isoleucine, threonine, serine, valine, alanine, or glycine.

13. The scaffold of claim 1 , wherein said beta strand domains have the amino acid sequences of: SEQ ID NO:239 for the A beta strand, SEQ ID NO:229 for the B beta strand, SEQ ID NO:230 for the C beta strand, SEQ ID NO: 236 for the D beta strand, SEQ ID NO:232 for the E beta strand, SEQ ID NO:245 for the F beta strand and SEQ ID NO:246 for the G beta strand.

14. The scaffold of claim 1 , wherein said beta strand domains have the amino acids of: SEQ ID NO: 239 for the A beta strand, SEQ ID NO:229 for the B beta strand, SEQ ID NO: 247 for the C beta strand, SEQ ID NO: 236 for the D beta strand, SEQ ID NO: 232 for the E beta strand, SEQ ID NO: 248 for the F beta strand and SEQ ID NO: 234 for the G beta strand.

15. The scaffold of claim 1 , wherein said BC and FG loops are non-naturally occurring variants.

16. The scaffold of claim 1 , wherein said BC, DE and FG loops are non-naturally occurring variants.

17. The scaffold of claim 1 , wherein the target is TRAIL-R2.