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another GST story #2

Tracy Aquilla aquilla at salus.med.uvm.edu
Tue Jul 19 17:24:56 EST 1994

In Article <Stephen_Lasky-1407940932390001 at tonto-slip8.cis.brown.edu>,
Stephen_Lasky at brown.edu (Stephen R. Lasky) wrote:
>In article <9407131615.AA04027 at hera.med.utoronto.ca>,
>emma at HERA.MED.UTORONTO.CA (Emma Macfarlane) wrote:
>Delete some stuff
>>The problem could be due to the
>> protein not folding properly I suppose and consequently not running as a
>> nice globular protein should on SDS-PAGE. 
>Delete some more
>> Sorry for the clutter
>> Emma
>I have been under the impression since my grad school days that proteins
>(after boiling in the presence of 2-mercaptoethanol and SDS) attain a
>relatively unfolded configuration and run as rods on SDS-PAGE.  I thought
>that this was the reason that sizes of proteins can be compared using the
>relative mobility on SDS-Page gels as opposed to native gels:  All the
>proteins have essentially the same shape as well as charge to mass ratio
>(due to the SDS).  I'd appreciate knowing if my impressions are incorrect.
>Stephen R. Lasky, Ph.D.       Brown University/Roger Williams Medical Center
>e-mail: Stephen_Lasky at brown.edu         LandLine: 401-456-6572
>America may be unique in being a country which has leapt from barbarism to
decadence without touching civilization:  John O'Hara

    In general this is true. However, proteins rich in proline residues
almost never migrate according to their predicted molecular weight, and
almost always migrate at a position corresponding to much larger proteins.
This may explain the observed phenomenon, however I do not know the amino
acid composition of these fusion proteins. If your fusions are high in
proline, expect them to migrate MUCH slower on PAGE gels than normal
proteins of the same MW.

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