Preparation of Thymus Alpha-actinin

Day 1-2

Materials

1. 0.5 mM PMSF, 4oC. Need 10 ml per gram tissue. Prepare by diluting 100 mM PMSF stock in 95% ethanol.

2. Buffer A: 1 mM EGTA, 0.5 mM PMSF, 2 mM Tris-HCl, pH 9.0 at 4oC, 20 ml per gram tissue.

3. Buffer B: 0.1 mM EDTA, 0.5 mM DTT, 0.02% NaN3, 10 mM Tris-acetate, pH 7.6 at 4oC, 7000 ml.

4. PBS solution A, 2000 ml, 4oC.

5. 0.5 M acetic acid for titration.

6. Ultrapure (enzyme grade) ammonium sulfate.

7. DE-52 column, 2.5x20 cm.

8. Scalpels and dissection scissors.

9. Miscellaneous glassware, 2-liter graduate cylinders, 4-liter beakers.

10. 2 GSA rotors and Sorvalls.

11. Waring blender, prechilled.

Procedure

1. Wash/rinse calf thymus in cold PBS. Remove fat and connective tissue. A typical preparation uses about 150 g (2-3 thymus, to fit into one GSA rotor). Extras can be stored frozen at -80oC. To use frozen gizzards, thaw for 1-2 hr in cold PBS at room temperature.

2. Homogenize in a Waring blender 3 times 10 sec bursts at high speed, in 10 volumes of 0.5 mM PMSF. Do this in the cold room.

3. Centrifuge in a GSA rotor at 12,000 rpm, 4oC for 60 min. Discard supernatant and floating lipids. Wipe lipids off the bottle.

4. Resuspend pellets in 10 volumes of buffer A at 4oC in a 4-liter beaker. Extract with gentle, constant stirring on ice for 1 hr. Check to make sure that pH is close to 9.

5. Titrate pH to 7.0 with 0.5 M acetic acid. Soak the electrode in high salt after use.

6. Centrifuge in a GSA rotor at 12,000 rpm at 4oC for 60 min.

7. Collect supernatant. Extract pellets as in steps 4-6, however extract for 40 min this time.

8. Pool both supernatants and measure volume.

9. Collect supernatnat and measure volume.

10. Bring ammonium sulfate to 15% saturation. Need 7.95 grams per 100 ml of volume in step 9. The crystals should be added slowly with constant stirring, while monitoring and maintaining pH at 7.0-7.2. Soak the electrode in high salt after this step.

11. Let stand on ice for 45 min after all ammonium sulfate has dissolved.

12. Centrifuge in a GSA rotor at 10,000 rpm, 4oC for 20 min.

13. Collect supernatant. Bring ammonium to 40% saturation as in step 10. Use 14.1 g per 100 ml as measured in step 9.

14. Let stand on ice for 45 min after all ammonium sulfate has dissolved.

15. Centrifuge in a GSA rotor at 10,000 rpm, 4oC for 20 min.

16. Resuspend pellets in 40 ml buffer B. Dialyze for 36 hr against 2 liters of buffer B, change buffer every 12 hr.

16. Equilibrate the DE-52 column with buffer B.

Day 3-4

Materials

1. Buffer B, 2000 ml, degased.

2. Buffer P: 0.2 mM DTT, 0.02% NaN3, 50 mM (KH2PO4+K2HPO4), pH 7.0 at 4oC, 5 liters.

3. Whatman GFC filters, funnel, side-arm flask.

4. Hydroxylapatite column (BioRad DNA grade Bio-Gel HTP), 2.5x40 cm.

5. Gradient maker, fraction collector and UV monitor.

Procedure

1. Collect solution from the dialysis bag. Centrifuge in a 50.2Ti rotor at 45,000 rpm, 4oC for 60 min. Discard milky portion of the supernatant.

2. Filter the supernatant through 2 layers of GFC filters under suction.

3. Clarify by centrifuging in a 50.2Ti rotor at 45,000 rpm, 4oC for 30 min.

4. Apply to the DE52 column equilibrated in buffer B.

5. Wash column with 100-200 ml buffer B or until OD drops to baseline.

6. Elute with 500 ml 0-450 mM NaCl gradient. Fill the mixing side of the gradient maker with 255 ml buffer B, the reservoir side with 245 ml buffer B with 6.5 g NaCl. Collect 3 ml fractions at 20-25 ml/hr. Set monitor full scale at OD 1.0, chart speed 1.5 cm/hr. Wash the column with 1 liter of 2 M NaCl in buffer B when finish.

7. Locate peak fractions. Run SDS-PAGE of various peaks. Pool alpha-actinin fractions towards the end of the gradient. Dialyze against 2 liters of buffer P for 24 hr. Change buffer at 12th hr.

7. Equilibrate the hydroxylapatite column with buffer P.

Day 5-6

Materials

1. Buffer P, 2000 ml, degased.

2. Buffer B without EDTA, 5000 ml.

3. 1 M (KH2PO4+K2HPO4), pH 7.0, 100 ml.

4. Ultrapure (enzyme grade) ammonium sulfate.

5. Sepharose 6B-CL column, 2.5x90 cm.

6. Gradient maker, fraction collector and UV monitor.

Procedure

1. Collect solution from the dialysis bag. Centrifuge in a 50.2Ti rotor at 45,000 rpm, 4oC for 1 hr.

2. Apply to the hydroxylapatite column equilibrated in buffer P. Wash with 50-100 ml buffer P or until OD drops to baseline.

3. Elute with 500 ml 50-300 mM phosphate gradient. Fill the mixing side of the gradient maker with 255 ml buffer P, reservoir side with 180 ml buffer P and 65 ml buffer 3. Elute at 20 ml/hr. Collect 3 ml fractions. Set monitor full scale at OD 0.5, chart speed 1.5 cm/hr. Wash the column with 1 liter of 500 mM phosphate in buffer P when finish.

4. Locate peak fractions and run SDS-PAGE. Pool alpha-actinin containing fractions (central peak). Measure volume.

5. Precipitate with 45% saturation ammonium sulfate (26 g per 100 ml).

The crystals should be added slowly with constant stirring, while monitoring and maintaining pH at 7.0-7.2. Soak the electrode in high salt after this step.

6. Let the solution stand on ice for 30-45 min after all ammonium sulfate has dissolved.

7. Collect precipitates by centrifugation in a SS34 rotor at 10,000 rpm, 4oC, for 20 min.

8. Resuspend pellets in 3 ml buffer B without EDTA. Dialyze against 2 liters of buffer B without EDTA for 24 hr. Change buffer at 12th hr.

9. Equilibrate Sepharose 6B-CL column with 1000 ml buffer B without EDTA.

Day 7-8

Materials

1. Buffer B without EDTA, 2000 ml.

2. 2 mM PIPES, 0.02%NaN3, 1500 ml.

3. Ultrapure (enzyme grade) ammonium sulfate.

Procedure

1. Collect solution from the dialysis bag. Centrifuge in a 50Ti rotor at 40,000 rpm, 4oC for 2 hr.

2. Apply to Sepharose 6B-CL column equilibrated in buffer B without EDTA.

3. Elute with maximum pressure. Collect 3 ml fractions. Set monitor full scale at OD 0.5, chart speed 1.5 cm/hr.

4. Run SDS-PAGE of peaks to locate alpha-actinin (central peak). Pool fractions and measure volume.

5. Precipitate alpha-actinin with 45% saturation ammonium sulfate (26 g per 100 ml).

6. Let the solution stand on ice for 30-45 min after all ammonium sulfate has dissolved.

7. Collect precipitates by centrafugation in a SS34 rotor at 10,000 rpm, 4oC, for 20 min.

8. Resuspend pellets in 400 µl of 2 mM PIPES with azide. Dialyze against 500 ml of this buffer. Change buffer twice over a period of 24 hr.

9. Clarify in a 50Ti rotor at 40,000 rpm, 4oC, for 45 min.

10. Store in liquid nitrogen as aliquots. Stable for months.


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