How to express toxic proteins in bacteria

Hui Wang wang.508 at
Wed Sep 13 02:10:08 EST 2000

Hi,  I am trying to express my favorite gene cloned in pET vector in
E. Coli BL21. The N-terminal truncated protein (missing 13AAs) can be
expressed to high level after 1mM IPTG induction for 2 to 4 hours.
However the full length protein can not be expressed at all. After the
2.5 ml overnight culture (some times this culture  grew fine) was put
into 50 ml LB, the bacteria grew very very slow as compared with the
truncated clone. I guess that the full length is toxic to bacteria,
but why its expression is not suppressed before adding the IPTG? How
can I completely suppress its expression (adding glucose or others?
how much?) so that the bacterial density can be high and then by
adding IPTG to expression my full length protein. I need your kind
help. Thanks 

Hui Wang

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