antibody crossreactivity problem

peter via (by peter.ianakiev from
Mon Jul 2 13:26:59 EST 2007

On Jul 2, 1:03 pm, Michael Sullivan <mlsul... from> wrote:
> I've prepared a rabbit polyclonal antiserum against a plant protein
> of interest. From immunoblots, it appears that the antiserum is
> crossreacting with the large subunit of Rubisco to make a big fat
> band. As many of you probably know, Rubisco is very prominent in
> extracts derived from green plant tissues and can constitute up to
> 50% of the protein in such a sample. Since the antigen was protein
> that was produced in bacteria, I think any cross reactivity must just
> be coincidental. Also, the pre-immune serum, did not have any problem
> with rubisco crossreactivity. I haven't found any obvious stretches
> of sequence similarity between rubisco and my protein of interest to
> account for the crossreactivity, but I think it can be hard to make
> predictions about antibody cross-reactivity based on sequence alone.
> Unfortunately, the protein I would like to detect with the antiserum
> is very similar in size to Rubisco. I'm worried I won't be able to
> detect "real" signal from my protein of interest because of the big
> fat Rubisco band.
> Has anybody had a similar problem, and if so, are there any
> solutions? Might different blocking agents help (I'm currently using
> 5% NFDM in TBS)? Can one do a more "stringent" wash to eliminate
> unwanted signals. Currently, I'm thinking the best strategy might be
> to express Rubisco in bacteria and use the lysate to preadsorb the
> antiserum.
> Useful comments would be much appreciated.
> Mike
> ---
> Michael L. Sullivan
> Plant Research Molecular Geneticist
> US Dairy Forage Research Center
> 1925 Linden Drive West
> Madison, WI 53706
> (608) 890-0046 (Phone)
> (608) 890-0076 (FAX)

Try 0.1 to 1% tween (or other non ionic detergent)  in TBS. Also look
for competition with the peptide to find out if this is specific/
nonspecific signal. Try also native vs SDS gel, one might work better
than the other.

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