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ThioFusion Expression System

Armin Sepp Armin.Sepp at bbsrc.ac.uk
Fri Dec 15 19:02:48 EST 1995

Groot at rulsfb.leidenuniv.nl (Pieterke) wrote:
>Who has experience with the ThioFusion Expression System for protein 
>purification, which is sold by Invitrogen? Is the fusion protein mainly 
>expressed in the soluble fraction? And is it possible to excrete the 
>proteins by osmotic shock treatment? And what is the best way to get rid 
>of the Thioredoxin in the protein mixture? Hopefully anyone can give me 
>some good advice. Thank you,
>			Pieterke
Dear Pieterke,
There does not seem to be any affinity tag in the ThioFusion vector as judged by their catalogue 
data. I've also noticed people saying earlier in this newsgroup that the expression levels are, as 
always, protein-specific. 
If it is of interest, then Novagen sells analogous system codenamed pET32 that in my case  helped 
to push up the level of expression from ca 50microg/l in the case of GST-fusion to ca 
500microg/l soluble protein. It is of interest that the optimal host in both cases was 
BL21(DE3)pLysS (Novagen) although the recommended strain for thioredoxin fusion is AD494. The  
fusion protein (containing three cysteins)was functionally active and could be purified from the 
lysis mix to relative homegeneity by Ni-affinity chromatography.

In summary, there does not seem anything that can be taken for granted, Screening a panel of 
vectors and hosts still seems the only option.

Good luck
(needless to say, I am just a customer for the named and impled companies....)
* Armin Sepp, PhD           \                                    *
* Department of Immunology   \     "Every little helps." (Tesco) *
* Babraham Institute          \                                  *
* Cambridge CB2 4AT,U.K.       \      Armin.Sepp at bbsrc.ac.uk     *

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