Protein don't migrate in SDS PAGE - my protein is wierd!! help!! (Feb/01/2006 )

Hi.

My protein (lane 2) is really wierd.

It is a purified His-tagged protein (N-terminal). It was expressed well in E.coli, and moderate in solubility (welll anyway it was seen on sds-page), and it was purifed with Ni-NTA and immidazol.

As you look at lane 2 in my figure,

i) migration progressed narrower than its well;
ii) smear appeared
iii) maybe large portion of the protein was stuck in the well
iv) this was supported by the Bradford assay, which showed strangely high concentration
(40 times more than lane 1 protein)

So I guess it's aggregated, but there was no precipitation in the protein solution.

How can i solve this problem? Because I have to do EMSA with this protein, I need this protein in native form.

Please help me. Thank you.