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toxcic genes

Francois Coulier coulier at infobiogen.fr
Sat Oct 5 01:48:10 EST 1996

On Fri, 4 Oct 1996, Tim Angelotti wrote:

> I am trying to clone a cDNA encoding a extracellular protein.  However, I 
> noticed that all of my positive clones (correct orientation) grew very 
> slowly and thus gave poor yields.  I am using Bluescript.  I suspect that 
> this sequence is toxic, and talking with  a few others working with this 
> gene confirmed it may be.  Now the question, what is toxic about it?  Is 
> it the sequence of nucleotides, or is it producing some of the protein 
> accidently and this is toxic, or is it most likely an alternate open 
> reading frame coming from another cryptic promoter?  I have heard all 
> three and was wondering if anyone could shed light on this.  If it is any 
> of the above, does this mean that any DNA I recover is most likely 
> screwed up, rearranged, and would using ABLE or TOPP cells from 
> Stratagene help?  
> Tim Angelotti
> TU Muenchen
> Institute for Pharmakologie
I once got a similar problem trying to express a growth factor in e.coli.
Using 35Smethionine pulse label, I figure out I had a very low expression
within 15 min after induction, and then nothing.
Removing the signal peptide solved my problem.
Hope this help.

Francois Coulier
INSERM Unite 119
27 bd Lei Roure
13009 Marseille

tel (33) 91 75 84 11 (October 18, 1996=> 33 (0) 4 91 75 84 11)
fax (33) 91 26 03 64 (October 18, 1996=> 33 (0) 4 91 26 03 64)
email: coulier at infobiogen.fr

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