Dear doc james

Even i have expressed and purified 5-7 proteins in BL21 cells... During the period i was successful in purifying  110KDa protein,, 

I think there is no fast rule,, So go for it,, best of luck 

Ajaz,

Thank you! Yes, I'm going to try. If that doesn't work, I'll just express it in Sf9 cells.

Dr. James,

These might encourage your work,

http://2013.igem.org/Team:Heidelberg/Project/Delftibactin

http://journals.iucr.org/d/issues/2006/10/00/gx5098/gx5098.pdf

It is protein-dependent but you can assume a general rule of 150 kDa as a limit.

Thilanka, thank you for the two paper suggestions. Channing, long time no talk! I kinda figured that 165 kDa was above or near an upper limit. Maybe sf9 cells, via baculovirus, or maybe pichia yeast. Thanks Channing, hope all is well in Chapel Hill.

If there is an upper limit, I haven't hit it yet.  I routinely express polyketide synthase proteins (from Streptomyces) in a BL-21 derived strain that are in the 265-290 kDa size range.  Interestingly, I get more soluble and overall protein when using the pTet promoter in low-copy plasmids rather than pET vectors.  Good luck!

All, I got that ~165 kDa protein expressed. Thank you!