Apparent MW of protein on PAGE gel

[Ron Beavis]

In article <1994Mar9.202838.15613 at wmichgw> ou_lehrman at wmich.edu (Russ_Lehrman) writes:
>  
>
>> A fusion protein I expressed in E. coli has a apparent MW on SDS-PAGE gel ~5
>> kdlager than it's calculated MW. This protein is 303 aa residues with
>> acalculated MW of 35 kd but it runs at 40 kd position on SDS-PAGE. The
>> proteinhas very high content of basic amino acids (32 lysines,  20 arginine
>> and 16histidines). My question is : does high content of basic residues make
>> aprotein run slower?I would apreciate very much any hints to my question.
>

It is not unusual for basic (or acidic) proteins to run on SDS-PAGE with
apparent MW's significantly different from their true chemical molecular
mass.  If you are really concerned about this apparent mass shift, send a
sample out for mass spectrometry.

Ron Beavis
Memorial University of Newfoundland