GST tag protein purification - (Apr/10/2008 )

Hi

I had a problem seeing an extra band in SDS gel after my purification step using GST 4B sepharose. My protein is around 30 kd and i could see an extra band around 26 kd (GST tag). I did the purification again to remove GST tag but still i could see the band. I was just wondering whats the reason for getting GST band and is there any way i can get pure protein.


Thanks,

rams

If your protein is essentially pure, apart from this 26 kDa band, run the solution down a gel filtration column. If it is GST (which I actually doubt), it will tetramerise, so it will go to~100 kDa. Other wise, if it is another protein that happens to co-elute (maybe it interacts with your protein), you should still be able to separate it from the 30 kDa target protein.

If you don't have gel filtration, try ion exchange.

Hi

Swanny,

Thank you so much for your information. Are you sure that the GST exist only in as tetramer but not as monomer. If thats the case then i have to think about that extra band.

Thanks,

rams