Method of protein purification from
The present disclosure provides methods for releasing intracellular proteins. The method allows isolation of the protein of interest from the cell without the requirement for mechanical disruption of the cells, without the need for isolation of the cells from the culture media, and without the need for removal of the cells from the culture media.
1. A method for releasing an intracellular protein of interest from a gram negative bacterial cell expressing the protein of interest, the method comprising:
(a) providing a culture of a gram negative bacterial cell expressing the intracellular protein of interest;
(b1) contacting the culture with an inorganic salt; holding the culture containing the added inorganic salt for at least 10 minutes; contacting the culture containing the added inorganic salt with a chelating agent; or
(b2) contacting the culture with an inorganic salt and a chelating agent;
(c) holding the culture containing the added inorganic salt and added chelating agent for at least 10 minutes;
(d) optionally adjusting the pH of the culture containing the added inorganic salt and the added chelating agent to a pH between 4 and 9; and optionally holding the culture containing the added inorganic salt and the added chelating agent for at least 15 minutes;
(e) contacting the culture containing the added inorganic salt and the added chelating agent with a detergent;
(f) holding the culture containing the added inorganic salt, the added chelating agent and the added detergent for at least 1 hour;
(g) optionally lowering the temperature of the culture containing the added inorganic salt, the added chelating agent and the added detergent;
(h) contacting the culture containing the added inorganic salt, the added chelating agent and the added detergent with a precipitating agent;
(i) holding the culture containing the added inorganic salt, the added chelating agent, the added detergent, and the added precipitating agent for at least 1 hour, and
(j) subjecting the culture comprising the added inorganic salt, the added chelating agent, the added detergent and the added precipitating agent to a method to remove a substantial portion of the cellular debris, thereby providing a supernatant composition comprising the protein of interest;
wherein the method does not comprise: (i) mechanical disruption of the cells, (ii) removing substantially all of the culture media, or (iii) addition of an enzyme that degrades cell wall material.
2. The method of claim 1 , wherein the method does comprise removing substantially all of the culture media.
3. The method of claim 1 , wherein the inorganic salt is selected from: sodium phosphate, ammonium sulfate, and sodium chloride.
4. The method of claim 1 , wherein the detergent comprises a detergent selected from the group consisting of: Triton, SDS, CHAPS 3, Nonidet P40, n-Octylglucoside, and Tween-20.
5. The method of claim 4 , wherein the detergent is a mixture of two detergents selected from the group consisting of: Triton, SDS, CHAPS 3, Nonidet P40, n-Octylglucoside, and Tween-20.
6. The method of claim 1 , wherein the precipitating agent is selected from a group consisting of: polyethyleneimine, and ammonium salt, and polyethylene glycol, TCA and ethanol.
7. The method of claim 1 , wherein the protein of interest comprises SEQ ID NO:1 or SEQ ID NO:2.
8. The method of claim 1 wherein step (c) is at least 20 minutes.
9. The method of claim 1 wherein step (d) is at least 30 minutes.
10. The method of claim 1 wherein step (i) is at least 30 minutes.
11. The method of claim 1 wherein step (i) is at least 30 minutes one hour.
12. The method of claim 1 wherein step (g) entails lowering the temperature below 25° C.
13. The method claim 1 wherein step (h) takes place at 20° C.-25° C.
14. The method of claim 1 wherein the salt of step (b1) or (b2) is at least at a concentration of 10 mM.
15. The method of claim 1 further comprising purifying the protein of interest from the supernatant of claim 1 (j) using chromatography.
16. The method of claim 1 , wherein the inorganic salt is sodium phosphate at 10 to 100 mM.
17. The method of claim 1 , wherein the chelating agent is EDTA at 75 to 200 mM.
18. The method of claim 1 , wherein the detergent is Triton X-100 at 5-8% and SDS at 0.05-0.2% percent.
19. The method of claim 1 , wherein the precipitating agent is polyethyleneimine at 0.5 percent.
20. The method claim 1 wherein step (h) takes place at 21° C.-22° C.
21. The method claim 1 wherein step (h) takes place at 22° C.
22. The method of claim 1 wherein the salt of step (b1) or (b2) is at least at a concentration of 10 mM.
23. The method of claim 1 wherein the salt of step (b1) or (b2) is at least at a concentration of 20 mM.
24. The method of claim 1 wherein the salt of step (b1) or (b2) is at least at a concentration of 30 mM.
25. The method of claim 1 wherein the salt of step (b1) or (b2) is at least at a concentration of 40 mM.
26. The method of claim 1 wherein the salt of step (b1) or (b2) is at least at a concentration of 50 mM.
27. The method of claim 1 , wherein the salt of step (b1) or (b2) is at least at a concentration of 60 mM.
28. The method of any of claims 8 , 13 , 14 and 16 - 19 , wherein the protein of interest comprises SEQ ID NO:1 or SEQ ID NO:2.
29. The method of claim 1 , wherein the protein of interest comprises SEQ ID NO:1 or SEQ ID NO:2, the inorganic salt is sodium phosphate at 10 to 100 mM, the chelating agent is EDTA at 75 to 200 mM, the detergent is Triton X-100 at 5-8% and SDS at 0.05-0.2% percent, and the precipitating agent is polyethyleneimine at 0.5 percent.
30. The method of any one of claim 1 , 2 - 6 , 7 - 14 , 15 - 17 , or 29 , wherein the gram negative bacterial cell is E. coli.