FLAG epitope and protein migration on PAGE

Glen Humphrey gwh at spam.block.cpcug.org
Sat Jun 10 17:11:02 EST 2000


On Fri, 09 Jun 2000 14:36:38 -0400, Deborah_Britt at brown.edu (Deb
Britt) wrote:

>I was wondering if anyone has ever noticed anomalous migration during PAGE
>of proteins tagged with the FLAG epitope.
>

Yes, adding the Flag epitope to a protein will often cause it to
migrate a little slower in SDS-PAGE. This is partly due to the
additional mass and partly due to the Flag sequence being rather
hydrophillic, such that it binds relatively less SDS than a "typical"
protein sequence of the same length. Other hydrophillic modifications
to proteins have the same effect, i.e. phosphorylation.

The reduced mobility caused by the Flag epitope can be an advantage,
if you want to distinguish the Flag-tagged recombinant protein from
its endogenous counterpart (i.e. expressed in transfected cells).

- Glen


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