Dimeric form of a protein? - I want my monomer! (Jan/18/2010 )
Hi!
I am trying to express a protein and I'm running SDS-PAGE to determine if I have achieved anything. After a few failed tests at different temperatures and IPTG concentrations, I tried a protocol for inclusion body purification to that point that I have dissolved any inclusion bodies, and then tested the results on a gel. Now, finally I get a clear band that hints I have actually got protein, but it is roughly at double the weight of what I expected, which leads me to suspect I have some sort of dimeric form.
Well, my question is if that could be a logical conclusion? I thought that the SDS usually separates dimers, and even when I have denatured with urea they seem to form the dimer. I have twelve extra amino acids from the expression vector that I will try to remove and I hope that does the trick, otherwise I'm in need of ideas..
Axel on Jan 18 2010, 08:33 PM said:
I am trying to express a protein and I'm running SDS-PAGE to determine if I have achieved anything. After a few failed tests at different temperatures and IPTG concentrations, I tried a protocol for inclusion body purification to that point that I have dissolved any inclusion bodies, and then tested the results on a gel. Now, finally I get a clear band that hints I have actually got protein, but it is roughly at double the weight of what I expected, which leads me to suspect I have some sort of dimeric form.
Well, my question is if that could be a logical conclusion? I thought that the SDS usually separates dimers, and even when I have denatured with urea they seem to form the dimer. I have twelve extra amino acids from the expression vector that I will try to remove and I hope that does the trick, otherwise I'm in need of ideas..
hey its quite possible that ur protein is actually showing anomalous mobility on the gel!. many proteins do show such profile coz of various reasons (highly acidic residues, hydrophobicity factors etc.)....i had a 27kDa protein running at 11kDa.........i think the best bet would be to confirm the identity of ur protein using western blot or mass spec.
You didn't mention that you tried any reducing agents....could you have disulfide bridges?