Different methods can be used to perform Cell lysis for protein
isolation and purification from Escherichia coli (E. coli) cells including
sonication, homogenization, enzymatic lysis chemical lysis and
freezing/grinding.
Ideally the perfect method has to be cheap simple, scalable, efficient
but also gentle to allow complete cell lysis but non-denaturing to preserve protein structure and function.
Unfortunately, in the real world, a
best universal method does not exist: each method has its pros and cons that make it
preferable on the basis of the amount of the cells and the number of samples to
be processed in parallel.
-The use of Freeze/Thaw (coupled or not with enzymatic lysis; eg Lysozyme supplementation) is preferable only when we have to manage an high number of small samples, the efficiency of this lysis approach decrease with increase in biomass:
- The sonication is the most used approach in lab scale to produce mgs of recombinant protein. Sonication can be used with biomasses from mg to 10-100g with a limited number of samples. With small biomasses up to 24 sample in parallel can be processed using a 24- probe sonicator – See Tips ofthe week #6)
The sonication cycle needs to be carefully optimized on the basis of the sonicator power, sonicator probe and sample volumes to obtain complete cell lysis but avoid localized heating within a sample that may induce protein unfolding and aggregation
- High pressure Homogenizers are the most commonly used devices used in industrial scale to lyse large quantities of bacteria but they do not allow to manage multiple samples in parallel.
- Combination of Chemical/enzymatic cell lysis could be an interesting option, alternative to the sonication, for all those projects (e.g protein production for microarray or preliminary crystallization screening with nanodrops) that require to produce in parallel limited amounts (0,5-1mg) of many different proteins.
Chemical lysis is generally
based on the use of moderate concentration of anionic or zwitterionic
detergents which are mild and therefore able to compromise the integrity of
cell membranes and facilitating lysis of cells and extraction of soluble
protein maintain their native form.
In the past I had the opportunity to use 2 different commercially products suitable for Chemical/enzymatic cell lysis:
CelLytic™Express (Sigma Aldrich cod. C1990 ) and B-PER in phosphate buffer (Thermo cod. 78266 )
CelLytic™ Express is a non-denaturing formulation including a zwitterionic detergent (CHAPS: 3,7-5% as reported in the formulation sheet), lysozyme and endonuclease applicable to protein extraction from E.coli before affinity purification (e.g. IMAC)
B-PER a non-denaturing formulation including a non-ionic detergent (unknown; non reported in the certificate of analysis provided in the Thermo website) in phosphate buffer. Prior use it has to be supplemented with lysozyme. DNase and MgCl2.
In some rare cases (as
the following) the Chemical_enzymatic Lysis was able to improve the protein
solubility respect than sonication
In my experience the
performances of CelLytic and B-PER are similar and which perform better is not
predictable but there are differences protein to protein, however If i have to
choose one of those, my first choice is the CelLytic which seem to have
slightly more frequently better impact on protein solubility.
N.B: Whatever method do
you like, remind to use the same method to evaluate protein solubility in the
small scale expression scale as well as you perform the scale-up protein purification.
DON’T use Chemical_enzymatic Lysis in small scale to screen solubility of a pellet just to save time and then perform the lysis of the entire biomass with sonication or high-pressure homogenizers because in some cases the results are not corresponding.
Pros
of CelLytic
- Simple and fast protocol:
1) Resuspend the CelLYtic powder
of a bottle in 25ml of water
2) Resuspend the E. coli
pellet adding 10ml of Celllytic/g E.coli pellet
3) Incubate 30 minutes at
RT under agitation. (Take sample for SDS page –> total fraction)
4) Centrifuge and filter surnatantthe
at 0.22um
5) Perform affinity purification (eg.IMAC)
- Do not require expensive instrumentation (eg Sonicator)
- Compatible with affinity purification (eh IMAC);
Cons of CelLytic
- Reagent is Expensive à 250ml of Cellytic cost about 230euro à 250ml for 25g of wet biomass
About 10 euro/gramm biomass!
- Sample is not directly appliable in SDS-page, because the presence of the detergent affects the sample run. The sample need to be diluted at least 4 time in a buffer (e.g. IMAC binding buffer) with-out detergents.
-
A great THANKS to
Roberta Cozzi that introdued me to
the use of CelLytic express and
Roberto Petracca that introduced me to the use of B-PER
!! Work
with both of them was a great pleasure !!
!! I miss a lot the 2 Ro’!!
