E.coli expression sysytems

iwilson at molbiol.ox.ac.uk iwilson at molbiol.ox.ac.uk
Sat Nov 6 09:27:16 EST 1993


In article <2b8qdj$pci at news.bu.edu>, pfoster at bu.edu (Patricia Foster) writes:
> 
> 
> 
>    I, too, get a contaminating band with my His6 construction using
> BL21(DE3) and Novagen's Ni resin.  I posted about it several months
> ago and got a few responses.  My band is about 43KDa.  It was suggested
> that it might be SOD (too small) or DNAK (too big).  Possibly it is
> DNAJ.  Interestingly, when I called Novagen, they denied that anyone
> else ever had this problem, but in one of their advertisements there
> is a clear contaminating band in their own gel.
> 
> Sincerely,
> 
> 
> --
> Patricia L. Foster
> Boston University School of Medicine
> Boston, MA USA
> pfoster at bu.edu

Our student actually got N-terminal sequence analysis run on her contaminant 
purified by the Ni-column, when attempt to purify her His6 construct from 
BL21. I have just run a BLAST analysis and the seqeunce corresponds to, 
surprisingly enough, an E. coli His-rich protein:

>gp|Z21496|ECHISRP_1 histidine rich protein [Escherichia coli]
            Length = 196

 Score = 136 (60.6 bits), Expect = 1.2e-12, P = 1.2e-12
 Identities = 29/30 (96%), Positives = 29/30 (96%)

Query:     1 MKVAXDLVVSLAYQVRTEDGVLVDESPVSA 30
             MKVA DLVVSLAYQVRTEDGVLVDESPVSA
Sbjct:     1 MKVAKDLVVSLAYQVRTEDGVLVDESPVSA 30  

Did anyone else get the same?

Iain Wilson
Dyson Perrins Laboratory, University of Oxford
iwilson at molbiol.ox.ac.uk



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