size of tagged proteins - (Jan/18/2007 )

Hi, Does anyone knows how big can a protein be to use a GST tag?. my protein is already 150 KDa nad it worries me to put an extra 26 there.
Thanks

GST's size is 26kDa. So the total of your recombinant protein will be 176 kDa. Hmmm I think it is alright to run a SDS with that by using high range protein marker. Broad range has maximum size around 200 to 250 kDa. But I think it is sufficient.
Again, it depends what you want to do with your protein. Cleave or not to cleave?

Hope it helps.

Thqanks timjim, i want to purify it , cleave it and assay it. i am worried also about the purification of such big protein , i hope doesnt aggregate. I laready tried histag and didnt work so i changed to gst.. but the size keeps concerning me

GST's size is 26kDa. So the total of your recombinant protein will be 176 kDa. Hmmm I think it is alright to run a SDS with that by using high range protein marker. Broad range has maximum size around 200 to 250 kDa. But I think it is sufficient.
Again, it depends what you want to do with your protein. Cleave or not to cleave?

Hope it helps.

No worries, I am new to this field, so if anything wrong, please point it out for me. Thanks.

Purify it? By using Sepharose for purification and later on using thrombin to cleave away the GST?

I think GST has its own protein activity so really have to cleave out. Unlike His Tag, it was claimed that it doesnt have any activity and the size is almost negligible.

I have to say, the size of your protein is pretty large. But I am sure it will be alright. =)