anomalous protein migration SDS-PAGE

awb at awb at
Fri Jan 27 12:13:14 EST 1995

In article <3g8d31$t46 at> lenny at (Lenny Garfinkel) writes:
>From: lenny at (Lenny Garfinkel)
>Subject: anomalous protein migration SDS-PAGE
>Date: 26 Jan 1995 14:54:25 GMT

>This group appears to be dead, but I guess I can't lose by posting.  I
>have a fermentation supernatant (does not matter what organism) which I
>suspect contains proteases.  When I add a pure protein to the sup and
>incubate for anywhere from 0.5 hr to overnight, I see an apparent
>INCREASE in molecular weight on SDS-PAGE in the presence of
>mercaptoethanol (yup, it runs slower).  What sort of protein
>modifications could cause this?  Could clipping of a few residues result
>in less SDS binding?

I guess that it could be due to either phosphorylation or possibly 
glycosylation, if the increase in mw that you see is small (2kDa or so in 
the case of glycosylation).  If you include some protease inhibitors you 
should be able to determine if your increase in mw is due to protease action, 
and of course you can always use a kit to see ig the glycosylation pattern has 

Hope this helps
Dr. Andrew Berry
Inst. of Biological Sci
Wales, UK.

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