PIWIL2
PDB:3QIR
Revision
Revision Type:created
Revised by:created
Revision Date:created
Entry Clone Accession:BC111751
Entry Clone Source:MGC CM30-G11 (BC111751)
SGC Clone Accession:PIWIL2_27; plate JMC037B01
Tag:N-terminal tag: MGSSHHHHHHSSGRENLYFQG
Host:BL21 (DE3) Codon plus RIL (Stratagene)
Construct
Prelude:Sequence:MGSSHHHHHHSSRENLYFQGRNDCVLDVMHAIYQQNKEHFQDECTKLLVGNIVITRYNNRTRIDDVDWNKTPKDSFTMSDGKEITFLEYYSKNYGITVKEEYDQPLLIHRPSERQDNHGMLLKGEILLLPELSFMTGIPEKMKKDFRAMKDLAQQINLSPKQHHSALE
Vector:pET28a-MHL
Growth
Medium:LB (Sigma L7658
Antibiotics:50 µg/mL kanamycin (BioShop Canada KAN 201)
Procedure:A 250 mL flask containing LB (Sigma L7658) supplemented with 50 µg/mL kanamycin (BioShop Canada KAN 201) was inoculated from a glycerol stock of the bacteria. The flask was shaken overnight (16 hours) at 250 rpm at 37 °C. Using the Lex system, a 2L bottle (VWR 89000-242) containing 1800 mL of TB (Sigma T0918) supplemented with 1.5% glycerol, 50 ug/ mL kanamycin and 600 µl antifoam 204 (Sigma A-8311) was inoculated with 50 mL overnight LB culture, and incubated at 37 °C. The temperature of the media was reduced to 18 °C one hour prior to induction and induced at OD
600 = 2 with 100 µM isopropyl-thio-β-D-galactopyranoside (BioShop Canada IPT 001). Cultures were aerated overnight (16 hours) at 18 °C, and cell pellets collected by centrifugation and frozen at -80 °C.
Purification
ProcedureIMAC: Unclarified lysate was mixed with 2-3 mL of Ni-NTA superflow Resin (Qiagen) per 40 mL lysate. The mixture was incubated with mixing for at least 45 minutes at 4 degrees Celsius. The mixture was than loaded onto an empty comLum (BioRad) and washed with 100 mL wash buffer.
Gel filtration chromatography: An XK 26x65 column (GE Healthcare) packed with HighLoad Superdex 75 resin (GE Healthcare) was pre-equilibrated with gel filtration buffer for 1.5 column volumes using an AKTA explorer (GE Healthcare) at a flow rate of 1.0 mL/min. The dialyzed sample from the IMAC step (approx. 15 mL) was loaded onto the column at 1.5 mL/min, and 2mL fractions were collected into 96-well plates (VWR 40002-012) using peak fractionation protocols). Fractions observed by a UV absorption chromatogram to contain the protein were pooled.
Extraction
ProcedureFrozen cell pellet contained in bags (Beckman 369256) obtained from 2L of culture were thawed by soaking in warm water. Each cell pellet was resuspended in 25-40 mL lysis buffer and homogenized using an Ultra-Turrax T8 homogenizer (IKA Works) at maximal setting for 30-60 seconds per pellet. Cell lysis was accomplished by sonication (Virtis408912, Virsonic) on ice: the sonication protocol was 10 sec pulse at half-maximal frequency (5.0), 10 second rest, for 10 minutes total sonication time per pellet.
Concentration:Purified proteins were concentrated using 15 mL concentrators with a 10,000 molecular weight cut-off (Amicon Ultra-15, UFC900524, Millipore) at 3750 rpm, typically resulting in a final concentration around 20 mg/mL.
LigandMassSpec:Crystallization:Before crystallization, crystals of human PIWIL2 PAZ domain was grown at 291 K using the hanging drop method by mixing equal volumes of 0.2 M NaI, 20% PEG 3350. The crystals were cryoprotected by cryoprotectant consisting of 100% reservoir solution plus 10% glycerol.
NMR Spectroscopy:Data Collection:Data Processing:
