Dr. S. Bhattacharya sbhattac at
Mon Jun 28 11:45:59 EST 1993

I'm affinity purifying a GST-fusion protein expressed in E.coli using a 
Glutathione-sepharose 4B matrix from Pharmacia.  I get a nice 52 kd band
which I've blotted and is a fusion protein as it is detected by an anti-GST
antibody.  I also get a 69 kd band co-purifying; this is not a fusion protein.
It does not appear when I express the GST alone. Changing the cell type
(DH5alpha and TOPP-1) does not affectit.  Washing the matrix (before elution)
with increasing stringency of NaCl (upto 1M) also does not help. Pharmacia
tell me that this hasn't been reported to them before. 

Has anyone else had a similar experience, I would be glad to hear.  Also any 
suggestions on how I can get rid of the extra band would be much appreciated.

Shoumo Bhattacharya
MRC Molecular Medicine Group
RPMS London

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