Crystallization of cathepsin S

1. A composition comprising a protein in crystalline form wherein the protein consists of SEQ ID NO:3, and wherein the protein crystal has a crystal lattice in a P4 1 22 space group and unit cell dimensions, +/−5%, of a=b=85.159 Å and c=152.18 Å.

2. A composition according to claim 1 wherein the protein crystal diffracts X-rays for a determination of structure coordinates to a resolution having a value that is less than or equal to 3.0 Angstroms.

3. A method comprising:

forming a crystallization volume comprising a precipitant solution and a protein that consists of SEQ ID NO:3, and wherein a protein crystal is formed that has a crystal lattice in a P4 1 22 space group and unit cell dimensions, +/−5%, of a=b=85.159 Å and c=152.18 Å; and

storing the crystallization volume under conditions suitable for formation of a protein crystal.

4. A method according to claim 3 wherein a protein crystal is formed that diffracts X-rays for a determination of structure coordinates to a resolution having a value that is less than or equal to 3.0 Angstroms.

5. A non-crystalline protein consisting of SEQ ID NO:3.

6. A non-crystalline protein consisting of residues 114-331 of SEQ ID NO:1.

7. An isolated non-crystalline protein consisting of SEQ ID NO:3.

8. An isolated non-crystalline protein consisting of residues 114-331 of SEQ ID NO:1.

9. A method for obtaining a three dimensional structure of a protein comprising the steps of:

(a) obtaining a crystal of a protein whose sequence consists of SEQ ID NO:3, wherein the protein crystal has a crystal lattice in a P4 1 22 space group and unit cell dimensions, +/−5%, of a=b=85.159 Å and c=152.18 Å;

(b) using the crystal obtained in step (a) to obtain an x-ray diffraction pattern; and

(c) solving the three dimensional structure of the protein from the diffraction pattern obtained in step (b), thereby obtaining the three dimensional structure of the protein.

10. A method for identifying a compound that binds to a protein comprising the steps of:

(a) obtaining a crystal of a protein whose sequence consists of SEQ ID NO:3, wherein the protein crystal has a crystal lattice in a P4 1 22 space group and unit cell dimensions, +/−5%, of a=b=85.159 Å and c=152.18 Å;

(b) using the crystal obtained in step (a) to obtain an x-ray diffraction pattern;

(c) solving the three dimensional structure of the protein from the diffraction pattern obtained in step (b), thereby obtaining the three dimensional structure of the protein; and

(d) identifying one or more compounds that binds to the protein based on the three dimensional structure.

11. The method according to claim 10 , further comprising the step of:

contacting one or more compounds identified in step (d) with the protein whose sequence consists of SEQ ID NO:3.

12. The method according to claim 11 , further comprising the step of:

measuring an activity of the protein whose sequence consists of SEQ ID NO:3, when the protein is contacted with the one or more compounds.

13. The method according to claim 12 , further comprising the step of:

comparing activities of the protein whose sequence consists of SEQ ID NO:3, when the protein is in the presence of and in the absence of the one or more compounds.

14. The method according to claim 10 , further comprising the steps of:

contacting one or more compounds identified in step (d) with a cell that expresses a protein whose sequence consists of SEQ ID NO:3; and

detecting whether a phenotype of the cell changes when the one or more compounds are present.