Entry Clone Source: MGC |
Entry Clone Accession: IMAGE:3357140 |
SGC Construct ID: ENOSF1A-c001 |
GenBank GI number: gi|3454185 |
Vector: pNIC28-Bsa4. Details [PDF ]; Sequence [ FASTA ] or [ GenBank ] |
Amplified construct sequence: |
Final protein sequence (Tag sequence in lowercase): ^ TEV cleavage site |
Tags and additions: N-terminal, TEV protease cleavable hexahistidine tag |
Host: BL21 (DE3)R3-pRARE2 (Phage resistant strain). |
Transformation: The construct DNA was transformed into competent cells of the expression strain by a standard heat shock procedure. |
Glycerol stock preparation: One colony from the transformation was used to inoculate 1 ml of TB media containing 50 µg/ml kanamycin and 34 µg/ml chloramphenicol, which was placed in a 37°C shaker overnight. The next day glycerol stocks were prepared from this overnight culture. |
Expression: A glycerol stock was used to inoculate 50 ml of TB media containing 50 µg/ml kanamycin and 34 µg/ml chloramphenicol, which was placed in a 37°C shaker overnight. The next day this starter culture was used to inoculate 12L of TB media (3.5 ml starter culture used per 1L) containing 50 µg/ml kanamycin. When the OD600 reached approximately 1.0 the temperature was reduced to 18°C and after a further 30 minutes the cells were induced by the addition of 0.1 mM IPTG. The expression was continued overnight |
Cell harvest: Cells were harvested by centrifugation at 6000 x g after which the supernatant was poured out and the cell pellet either placed in a -20°C freezer or used directly for purification. |
Cell Lysis: Cell pellets were dissolved in approximately 150ml lysis buffer and broken by homogenization by 5 passes at 12,000 psi. The cell debris was pelleted at 35,000 x g and the supernatant used for further purification |
Column 1: Ni-NTA (2.5 ml volume in a gravity-flow column). |
Column 1 Buffers: |
Column 1 Procedure: The clarified cell extract was incubated with 2.5 ml of Ni-NTA pre-equilibrated with lysis buffer for 1 hour at 4°C with rotation after which it was passed through a glass column. The column was then washed with Binding Buffer (60 ml) and Wash Buffer (50 ml). The protein was eluted with 25 ml of Elution Buffer in 5 x 5 ml fractions. |
Column 2: Gel filtration, HiLoad 16/60 Superdex S75 prep grade, 120ml (GE Healthcare). |
Column 2 GF Buffer: 10 mM Hepes pH 7.4, 500 mM NaCl, 0.5 mM TCEP, 5% Glycerol |
Column 2 Procedure: The wash buffer fractions and elution buffer fractions from column 1 were pooled separately and concentrated to 5 ml with a 30 kDa mwco spin concentrator and injected onto an s200 16/60 column (pre-equilibrated in GF Buffer) at 1.0 ml/min. 1.0 ml fractions were collected. |
Column 3: TEV cleavage/ Ni-NTA rebind. |
Column 3 Wash Buffer: 10 mM Hepes pH 7.4, 500 mM NaCl, 0.5 mM TCEP, 5% Glycerol |
Column 3 Procedure: Protein from fractions eluted at 80-90 ml from s200 gel filtration were pooled and incubated with 1:20 mol:mol TEV protease overnight at 4°C. Then protein plus TEV was passed through a column containing 0.5 ml Ni-NTA pre-equilibrated with GF Buffer. Column was washed 2ml of GF Buffer and 2ml Elution Buffer. Protein was poorly cut and the majority of protein was found in the Elution buffer fraction.. |
Column 4: 1ml Resource Q Cation Exchange |
Column 4 Buffer A: 50 mM Tris pH 8.5, 50 mM NaCl |
Column 4 Buffer B: 50 mM Tris pH 8.5, 2 M NaCl |
Column 4 Procedure: Protein from Ni-rebind elution, approximately 4 ml, was diluted to 40 ml using Buffer A and injected into a 1ml Resource Q column. Protein was eluted using a linear gradient of 0-25% Buffer B over 35 column volumes at 1ml/min. 1.0 ml fractions were collected. |
Concentration: The fraction that was found in the flow-through was concentrated to 35 mg/ml using a 30 kDa mwco concentrator |
Mass spectrometry characterization: |
Crystallisation: Crystals were grown by vapour diffusion in sitting drop at 20°C. A sitting drop consisting of 100 nl protein and 50 nl well solution was equilibrated against well solution containing 25% (v/v) PEG3350 and 0.1 M Bis-Tris pH 5.5. Crystals were mounted in the presence of 25% (v/v) ethylene glycol and flash-cooled in liquid nitrogen. |
Data collection: |