GRA1 expression - elongation of the protein (Dec/31/2004 )

I work with T. gondii GRA1 protein expression. I am using Rosetta PlySs strain with pET vector and an other vector with CMV promoter with HEK cells. My problem is: My protein is 6-7 kDa bigger in SDS and WB in rosetta cells. But when I take human cells and lyse them the protein has the right size. So Why this happens with rosetta cells?

Hello,

Recombinant protein can give your on SDS PAGE bigger or smaller size some times. It can be caused due to tag influence (in case of fusion proteins) or many others factors. To be sure that you really have the protein with bigger molecular weight send it to Mass Spectrometry and check MW from this technique.

Alexei