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no expression of my protein - (Feb/06/2009 )

I was trying to test the expression of a dimer (AB), one (A) with Histag, the other (:D without. I also created a disulfide bond between A and B to stabilize the dimer.

The cloning was very successful. A and B are on different vectors, hense different antibiotics. I co-reansformed them into BL21(DE3) STAR.
I picked up one colony and grew in 5ml LB at 37C overnight. Then I inoculated 1ml O/N culture into 200ml LB, added IPTG to 1mM when the OD600 reached 0.6. Expression was at 22C O/N.

The next day, I did purification under denaturing condition (since I have already tried under native condition and got nothing). I didn't elute the proteins and just ran the beads. However I did not see bands for my proteins on SDSPAGE. I also ran pre-induction sample, lysate, flow-thought sample, and didn't see right-sized bands for my proteins.

What are potential pitfalls in protein expression? or, maybe I just picked up a wrong colony.....



Do you see any expression when you transform them independently?

The problem is expression or coexpression?


-T C-