Protocol 020 - TBXT expression and purification
Introduction
Brachyury purification protocol adapted from the Structural Genomics Consortium protocol in the TBXT TEP.
Materials
Procedure
pET3a TBXT G177D plasmid - synthesized at GenScript
Transform E. coli BL21 pBirA
b. Add 1 uL plasmid to bacteria
d. Incubate on ice for 30 min
e. Heat shock at 42C for 45 sec
f. Add 500 uL Terrific Broth (no antibiotics)
g. Culture at 37C, 250 rpm for 1 hr
h. Spin at 8,000 x g, 30 sec
i. Resuspend in 100 uL Terrific Broth
j. Plate and spread on LB + Ampicillin (100 ug/mL) + Spectinomycin (50 ug/mL)
k. Incubate plate at 37C overnight
l. Inoculate 5 mL Terrific Broth (Amp, 100 ug/mL; Spectinomycin 50 ug/mL)
m. Culture at 37C, 225 rpm for 16 hours
n. Prepare a glycerol stock for each bacterial strain
- Dilute 0.5 mL of the bacterial culture into a sterile 50% glycerol solution
Streak out the BL21 pBirA + pET3a-TBXT G177D on LB plate (Amp, 100 ug/mL; Spec 50 ug/mL)
a. Culture at 37C overnight
Inoculate a starter culture of 5 mL Terrific Broth (Amp, 100 ug/mL; Spec 50 ug/mL)
a. Culture in a shaking incubator at 37C, 22overnight (16 hours)
The follow day, prepare a 100 mM biotin stock solution
a. Prepare 2M ammonium hydroxide in dH20 from 28-30% stock (14.8M)
Dilute starter culture in 1L or 500 mL Terrific Broth (Amp, 100 ug/mL; Spec 50 ug/mL) in baffled flasks
a. Add biotin to 100 uM final concentration to the culture
Culture bacteria at 37C, 220 rpm until OD600 = 1.0
a. Move the baffled flasks to the bench for 10 min
Lower the incubator temperature to 30C or move to an shaking incubator pre-set at 30C
a. Add IPTG (1M stock) to 300 uM final concentration
Culture bacteria at 30C, 180 rpm for 3 hours
a. Spin cultures at 4,100 x g for 10 min
b. Decant supernatant and freeze the pellet at -20C
Thaw bacteria pellets on ice
Resuspend the pellets from 4 x 500 mL cultures in 40 mL ice-cold lysis buffer and transfer to a 50 mL conical tube
One tab of Roche cOmplete midi protease inhibitor
Sonicate in an ice water bath
a. 5 sec on and 10 sec off for 30 min
Transfer the lysate to two 50 mL Oakride centrifuge tube
Centrifuge at 10,000 rpm for 30 min at 4C
Wash Nickel agarose beads (50% slurry)
a. Pipet 2 mL of Nickel agarose bead slurry into a 50 mL conical tube
b. Add 10 mL of lysis buffer and mix well
b. Spin 250 x g for 1.5 min at 25C
c. Repeat twice more for a total of three washes
d. Keep on ice until the next step
Collect the lysate supernatant and transfer to the Nickel agarose beads
a. Batch bind on a rocker at 4C for 1 hour
Transfer the lysate and beads to a Bio-Rad gravity column (2.5 x 20 cm)
a. Pre-wash the gravity column with 25 mL of lysis buffer
Collect the flow through and save for analysis
Wash with 2 x 10 mL lysis buffer + 10 mM imidazole
Wash with 20 mL lysis buffer + 30 mM imidazole
Wash with 20 mL lysis buffer + 60 mM imidazole
Elute with 10 mL lysis buffer + 100 mM imidazole
Elute with 10 mL lysis buffer + 200 mM imidazole
Elute with 10 mL lysis buffer + 300 mM imidazole
Elute with 10 mL lysis buffer + 500 mM imidazole
Dilute 65 uL of each sample into 35 uL 4x LDS / 10x Reducing Agent master mix
Resolve samples in a 4-12% Bis-Tris SDS PAGE gel
b. Run the gel at 200V for 1 hour
Remove the gel from the case and incubate with Coomassie Stain Solution for 1 hr at 25C on rocker
a. Collect the Coomassie Stain Solution for reuse
b. Add ~ 25 mL destain solution
c. Knot a kimwipe and place in the corner of the box, replacing the kimwipe as needed
b. When the gel is fully destained, rinse twice with dH20 and image on the Odyssey LiCOR
Prepare 2L of dialysis buffer and chill to 4C
Concentrate Elutions 1-3 using an Amicon Ultra-15 10K filter
a. Spin at 3,500 x g for 15 min at 4C
b. Decant concentrated sample back into elutions
c. Add back to filter and spin again
d. Repeat a third spin until you have ~ 7-8 mL of solution remaining
* Do not over concentrate the protein -- keep protein concentration < 2 mg/mL
Transfer protein solution to a 15 mL conical on ice
Add 25 uL New England Biolabs TEV protease (10,000 U/mL stock) and mix gently
Cut Snakeskin Dialysis 10K MWCO tubing and wet the tubing in the dialysis buffer
Clip one end and add the protein to the tubing while the bag rests in the buffer
Clip the other end at the top, briefly turn the clipped tubing upside down to mix and ensure it does not leak
Dialyze overnight (at least 16 hours) at 4C
Equilibrate fresh Nickel agarose beads
a. Wash 2 mL of Nickel agarose slurry with 10 mL lysis buffer
c. Repeat twice more for a total of three washes
Collect dialyzed sample (~8 mL) and add directly to washed Nickel agarose beads
a. Invert tube several times to mix thoroughly
Incubate on ice for 20 min
Transfer protein solution and beads to Bio-Rad gravity column
a. Collect the flow through for all subsequent steps
Wash with 2 x 10 mL lysis buffer + 10 mM imidazole
a. Add the first 10 mL lysis buffer to the conical that contained the nickel agarose beads to collect any residual protein
b. Transfer gently to the column - do not disturb the beads on the bottom of the column
c. Use the second 10 mL lysis buffer to wash the column again
Wash the column with 2 x 10 mL lysis buffer + 30 mM imidazole (cleaved brachyury will be here)
Wash the column 2 x 10 mL lysis buffer + 60 mM imidazole (cleaved brachyury will be here)
Elute with 10 mL lysis buffer + 100 mM imidazole
Elute with 10 mL lysis buffer + 200 mM imidazole (His-GST and His-TEV will be here)
Elute with 10 mL lysis buffer + 300 mM imidazole (His-GST and His-TEV will be here)
Elute with 10 mL lysis buffer + 500 mM imidazole
Dilute 0.25% of each wash and elution sample into 4x LDS/10x reducting agent master mix
a. Load samples into a 4-12% Bis-Tris SDS-PAGE gel
b. Run the gel at 200V for 1 hr
Remove the gel from the case and Coomassie stain for 1 hr at 25C as above
Destain during the day or overnight, changing a knotted kimwipe in the corner as needed
a. The cleaved protein will be in the washes containing 30 mM and 60 mM imidazole
Concentrate the 4 x 10 mL washes containing cleaved brachyury using Amicon Ultra-15 10k filter
a. Wash the filter with 10 mL gel filtration buffer
c. Add 15 mL of washes at a time
d. Centrifuge at 3500 x g for 15 min at 4C
e. Add more washes to the filter, mix up and down
f. Repeat until you have ~ 1 mL remaining
Prepare buffers below and pass through a 0.22 um filter
a. 500 mL 20% ethanol in dH20
b. 500 mL Gel Filtration Buffer
50 mM HEPES pH 7.5, 500 mM NaCl, 5% glycerol, 1 mM TCEP
Turn on the Akta Prime Plus
Place the HiLoad Superdex 16/600 200 pg (lot 10330772) column on the Akta and connect the tubing drop-to-drop
Flush the system with 20% ethanol
a. Move both tubes into the 20% ethanol
c. Wash the system with 50 mL 20% ethanol at 50 mL/min -- 1 min
d. Set pressure alarm to 0.25 psi
a. Transfer #1 tubing to Gel Filtration buffer
b. Select inject mode, set parameters
- 1 mL/min (120 mL bed volume)
- Pressure alarm 0.25 psi
- Do not collect fractions
- Run the system ensuring the waste tube is in the collection bin
- Allow equilibration to flow for 120 min
Load the concentrated protein
a. In Load Mode, wash the 1 mL sample loop with 5 mL of Gel Filtration buffer
b. Spin concentrated protein from Step 56 in a Costar Spin-X 0.22 um cellulose actetate centrifuge tube filter at 25C
- Add 500 uL of protein sample to tube and spin at 6,000 x g for 15 sec at 25C
- Repeat with remaining 500 uL of protein sample
Collect 1 mL of filtered protein sample in 1 mL syringe using an injection needle (0.70 diameter)
In Load Mode, inject the protein into the sample loop
Inject the column and run the injection program
Move fractions 36-43 onto ice as available
Dilute 20 uL in 4x LDS/10x reducing agent master mix (40 uL total)
Load 40 uL of each sample into a 4-12% Bis-Tris SDS-PAGE gel
a. Run the gel at 200V for 1 hr
Remove the gel from the case and Coomassie stain and destain as above
Concentrate Fractions 38-40 using a Amicon Ultra-4 10k filter
a. Wash the filter with 4 mL gel filtration buffer
c. Combine fractions 38-40 into one vial
d. Add 4 mL of the fractions at a time
e. Spin at 3500 x g for 10 min at 4C
f. Add more of the fractions to the filter, mix up and down
g. Repeat until you have ~ 1.5 mL remaining
Measure protein concentration using a Nanodrop or Pierce Rapid Gold BCA protein assay kit