What factors effect protein migration on SDS-PAGE

[gc]

In article <961208101651.222212d4 at chemvx.tamu.edu>, KHUANG at CHEMVX.TAMU.EDU
wrote:

* Hi, Netters,
* I remember there had some discussion about protein migration on SDS-PAGE, but 
* I could not pick them out. I have a few expressed protein in hands, some show 
* higher molecular weight than predicted (from amico acid), some show lower M.W.
* It is said the hrdrophobic region in the protein effect protein migration on 
* SDS-PAGE, what are other factors?
* Thanks
* 
* Huang

I believe that there is some secondary structure left in the proteins even
in SDS-PAGE conditions.  I have a protein which undergoes proline
isomerization that causes it to migrate differently in the gel.  Also,
mutating 5 amino acids to alanines (don't remember what they are but they
are neither highly charged nor highly hydrophobic) in this protein causes
a noticable change in the way it runs while lots of other mutations have
no effect.

--Gene Cutler