Protein size in the SDSPAGE gel is different from the estimated size

Mitchell Isaacs misaacs at spam_me_not.student.usyd.edu.au
Thu Jun 21 02:34:16 EST 2001

"Hicham Zegzouti" <zegzouti at nature.berkeley.edu> wrote in message
> Hi everybody,
> I am working on a protein whose estimated MW (from cDNA )is 120KD. I
> overexpressed this protein in E.coli and made an antibody against it.
> Until now normal!
> After purifying the Antibody using Affigel coupled to my protein and
> using this purified Ab aginst transferred plant protein extract, I
> obtain a signal just at around 90 KD. Does anybody have seen
> something like this and does anyone have an explanation for it. What
No problems with that - the theoretical MW often doesn't correspond to the
gel location. Proteins are not as regular as DNA - so don't migrate as
predictably. You could be seeing a fragment - part of the protein may have
been cleaved. Also - have you checked for alternate start positions?

> do you think I can do to check that the band on the western
> corresponds to my protein?
Mass spec, or partial sequencing? Other properties you might know?
(hydrophobicity, absorption spectra).


More information about the Proteins mailing list

Send comments to us at biosci-help [At] net.bio.net