BL21pLysS and BL21

redeamer alion85 at
Fri Feb 6 06:40:13 EST 2004

Hi, Björn!

The main difference between those two guys is that pLysS strain has a
plasmid encoding Lysozyme that allows you to express more toxic
proteins in greater amounts... moreover, when you begin your
purification of desired proteins, the lysis of bacteria is greatly
enhanced compared to ordinary BL21, cause Lysozyme comes out and begin
lysing cells in addition to your method of disrupting (French press,

About induction, well, you use pET system as i can imagine, cause in
that system T7 promoter is leaking, and is not fully downregulated by
lac repressor, so i suppose you have a toxic protein... if upon
induction you ll get smaller yields... think you should use pLysS...
however, your sources tell that you should use plain BL21... so i am
in a guess, and may be it is wrong

for example if you want really  to control your protein expression
then you should use QIAGEN pQE system with T5 promoter that is VERY
VERY strict... and no or very very minimal leaking occurs, then at
least you can rule your cells yourself:) expression::)

by the way how do you select the cells without pLysS plasmid??? my
mind doesnt work anymore now, so i would like to get just a plain

Thank You in advance...

----------> Drew

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