Toxic protein for E. coli (M15)

Duncan Clark junk at
Thu Sep 5 06:05:45 EST 2002

Historians believe that in newspost <3D77151C.F3347BF1 at> on 
Thu, 5 Sep 2002, Bertrand Collet <b.collet at> penned the 
following literary masterpiece:
>I use the pQE30 expression vector in M15 bacterial strain.
>I noticed that the growth rate of the bacterial cultures is the same
>without inducer for pQE30 only and for pQE30 expressing my protein.

So your clone is correctly switched off.

>However, when I induce with IPTG (1mM) pQE30 continue to grow normally

Souns right, pQE30 isn't expressing anything yet.

>but my expression plasmid culture grow very very slowly:

So you are getting something expressed. It is not surprising to see a 
slow down in growth upon induction. It will vary expressed protein to 
expressed protein. Have you monitored expression by SDS PAGE  i.e. 0 
hours, 1hour, 2, 3 4 etc. after induction?

>It appears that
>my protein is toxic for E. coli but that I do not have any leaking

Do you get an extra protein band produced for your protein in your pQE30 
clone as opposed to pQE30 alone?


I love deadlines. I especially like the whooshing noise they make as
they go flying by.

Duncan Clark
GeneSys Ltd.

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