Wiki/Team:Warsaw/protocols

Purification of His_Z_alpha and His_Z_omega

Culture E. coli producer strain in 3 ml of liquid LB medium + kanamycin for 8 hours. Then use it to inoculate 200 ml of liquid LB medium + kanamycin supplemented with 0,5 mM IPTG and grow it overnight. In the morning spin down the culture (5000 RPM, 10 min, 4°C). Resuspend the pellet in PBS buffer and disrupt cells by sonication. Spin down sonication mixture (13200 RPM, 10 min, 4°C) and discard supernatant – protein is present in sonication debris. Resuspend it in sterile ice cold ddH2O and Spin down (13200 RPM, 10 min, 4°C). Discard supernatant and resuspend it in sterile ice cold ddH2O and store at 4°C.

Culture, induce and disrupt E. coli in the same way as to purify His_Z_alpha. The protein is present in supernatant (about 10% of total protein) and can be added to selection medium without further purification. Nevertheless we purified it to determine how much exactly should be added:

1. Swinging of sonication products with Ni-nta-agarose bed for 2 hours at 4°C
2. Loading onto column
3. Washing of the bed with 20 mM imidasole buffer
4. Elution with 100 mM imidasole

1. Setup of culture E. coli carrying "hunter" with kanamycin and 0,2 mM IPTG
2. Inoculate liquid LB medium with kanamycin, 50 μg/ml ampicylin, 0,2 mM IPTG and "prey" (the control is medium without "prey")
3. Grow it 4-16h
4. Observe growth, or its lack
5. Plasmid DNA isolation
6. Control digestion

We use "Plasmid Mini" plasmid DNA isolation kit from A&A Biotechnology and follow the protocol of producer.

We use "Gel-Out" DNA isolation kit from A&A Biotechnology and follow the protocol of producer.

We use "Clean-Up" DNA purification kit from A&A Biotechnology and follow the protocol of producer.

We use "Genomic-Mini" universal genomic DNA isolation kit from A&A Biotechnology and follow the protocol of producer.

Overall volume of digestion mix is either 20 μl, either 50 μl in case of digesting for ligation. We usually use 1 μl of restriction enzyme and the buffer in 10x dilution (as they initially are 10x concentrated). The rest of mix is plasmid DNA.

Keep the bacteria on ice during the procedure. Pour ca. 25 ml of bacteria into a falcon tube and spin in 4°C at 4 krpm, 8 min with prolonged acceleration and deceleration. Remove supernatant. The pellet mustn't run dry. You can pour another portion of bacteria onto it and spin again. After desired amount of bacteria in pellet is collected, add CaCl₂ in an amount of 10% of initial culture used for spinning. Suspend the pellet until no debris is visible on the bottom. Incubate 45 min on ice. Then spin 8 min at 4 kg and remove supernatant. Suspend the pellet in 3 ml CaCl₂ and divide into aliquots of 100 μl.

• Set up bacterial culture in 10 ml.
• Use the culture for inoculation of 1 L of medium and let it grow at 18°C until it reaches OD 0.6 - 0.8.
• Spin for 10 min at 6 krpm.
• Remove supernatant and suspend the pellet in 1 L of H₂O.
• Spin for 10 min at 6 krpm.
• Remove supernatant and suspend the pellet in 1 L of H₂O.
• Spin for 10 min at 6 krpm.
• Remove supernatant and suspend the pellet in 0.5 L of H₂O.
• Spin for 10 min at 6 krpm.
• Suspend the pellet in 20 ml 10% glycerol.
• Spin for 10 min at 6 krpm.
• Suspend the pellet in 3 ml 10% glycerol.
• Divide into aliquots of 40 μl and freeze in liquid nitrogen.

• Pour 100 ml H₂O plus desired amount of DNA into electroporation cuvette.
• Add 40 ul of bacteria.
• Electroporate.
• Add 0.5 ml of LB.
• Incubate with shaking at 37°C.
• Plate.

Add desired volume of DNA to the 100-μl-culture in eppendorf tube. Incubate 30 min on ice. Heat shock for 90 s at 42°C. Incubate 10 min on ice. Add 0.9 ml of culture medium and let the bacteria grow at 37°C.

We use the following mixture:

1. appropriate volumes of vector and insert DNA (usually concentration of insert 3X higher than that of vector)
2. 2 μl of ligation buffer
3. 1 μl of T4 DNA ligase (purchased from Fermentas)
4. nuclease-free water

Overall mix volume is 20 μl.
If ligated DNA has sticky ends - incubation durates 2h in room temperature; if ligated DNA has blunt ends - overnight incubation in 18°C.

Prepare digestion mix in overall volume of 50 μl.
Add to reaction mix:

• 1,5 μl of 2 mM dNTPs
• 0,5 μl Klenow fragment (for 5' sticky ends)
• 0,5 μl T4 DNA polymerase (for 3' sticky ends)
• Incubate overnight in 37 degrees.

Ampicillin
100 μg/ml for high copy number plasmids (pET15b)
30 μg/ml for one-copy plasmid (pZC320)
50 μg/ml for testing various hunter/prey combinations

Tetracycline
12-15 μg/ml

Kanamycin
30 μg/ml

Rifampicin
300 μg/ml

X-Gal
40 μg/ml

IPTG
For liquid LB broth: variable concentration, depends on induced protein
For plates (blue-white screening): 0.1 mM

1. Transform competent E. coli GM2163 cells with:
   
   • pMPMT5:AID,
   • pMPM:AT6,
   • pMPM:A+T13,
   • pMPM:A+AT,
   • pMPM:T7,
   and plate on LB + Amp 30 μg/ml + Tet.


2. Inoculate two tubes with 3 ml LB + Amp30 μg/ml + Tet + 100 μl of 20% L-arabinose with colonies of transformants (negative control without arabinose)
3. Incubate overnight in 37°C
4. Plate 200 μl of bacterial culture on LB + 300 μg/ml Rifampicin + Tet
5. Incubate overnight in 37°C.

1. Make digestion mix in overall volume of 50 μl.
2. Add 1 μl of Calf Intestinal Alkaline Phosphatase to the reaction mix.
3. Incubate 2h or overnight in 37°C.

1. Single transformations of competent E. coli GM2163 carrying plasmid pZC320 with:
   
   • pMPM T5-AID
   • pMPM AT6 (transcriptional fusion)
   • pMPM A+T13 (translational fusion)
   • pMPM T7
2. Induction using of L-arabinose (100 μl 20% inductor/3 ml LB broth Ap 30 μg/ml + standard Tet) and negative control of each probe
3. Plasmids' isolation (pMPM T5-AID, pMPM AT6 (transcriptional fusion), pMPM A+T13 (translatiomal fusion) and pMPM T7)
4. Transformations of competent E. coli TOP10 with the isolated plasmids
5. plating on TAXI (Tet+Ap 30+X-Gal+IPTG)

1. Place 10 μl of sample in a cuvette. Use 10 μl of solution, in which the sample is suspended, as control.
2. Mix BCA (bicinchoninic acid) with CuSO₄ (concentration?) in of 50:1 ratio.
3. Add 1.99 ml of BCA with CuSO₄ to the cuvettes.
4. Incubate 30 min at 37°C.
5. Measure absorbance at 562 nm.
6. Read protein concentration from reference curve.