[brijnbhatt]

Dear Ikariotis,

I saw your post just now, I am a molecular biologist and I have tried expression of many mammalian proteins in bacterial system. I found expression will depend upon many factors and not only expression media.
Expression media like TB and LB broth are good for expression.

You may also try-
1- Expression at three different temperatures that is 18, 25 and 37 degree Centigrade.
2- Different time for expression 4 hours, 8 hours and 16 hours.
3- Increase the amount of inducer and try!!!
4- If the protein has any co-factor like Zn, addition of salt related to Zn, like ZnCl2 may help to get better expression.

But I believe that vector system and Host cells are the main issue to get a expression of foreign gene in E. coli system.

BL21 lambda DE3, Rosetta cells etc., may be tried for expression. You must try pET system, pGEX and pQE vector are not good.

When I used some of the mammalian gene, first time I did not get any expression then we have to clone it in many vector systems, some were with tag and some of them without any tag. we have also tried PelB sequence at N and C terminus, we found addition of PelB sequence helps to get better expression and it get auto cleaved, so you may not need to worry about the additional sequence.

I have found hydrophobicity, trans-membrane domain and composition of Amino acid also matters. Proteins with high number of Proline amino acid residues are difficult to express.

Some of the proteins are stable only after formation of di-sulfide bonds and when you express them in bacteria they are not stable. Some of the E coli strains are available in market which makes stable to these proteins.

I would suggest you to get a detail analysis of your protein before selecting a system for expression.

If you have antibody for this protein you may do the western blot and check if it is detectable by western. It will help you to troubleshoot your problem.

Wish you all the best.

Dr. Brijesh N Bhatt