BL21 expression host
klenchin at REMOVE_TO_REPLY.facstaff.wisc.edu
Wed Feb 7 15:19:05 EST 2001
DOCTORHIM at aol.com wrote:
:The expression of T7 polymerase in BL21(DE3) is very leaky. Many clones
:don't even require induction for high level expression. Glucose will not
:help, as the promoter for the polymerase is lacUV5 which is a catabolite
:insensitive promoter. This is probably the reason it is so leaky.
True but I would put it conditionally - "can be very leaky". With some
proteins I don't even need to add IPTG to get optimal expression, while
with others it seems to be tight enough so as I do not see the major
band by coomassie staining. I don't understand where the difference
is coming from.
Using DE3 with pLys S or E usually helps but frequently at expense
of expression levels.
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