Hi Nick,
In the past, I've successfully expressed a 130 kd eukaryotic
protein in large quantities in plain BL21. I don't think size per se
is a major problem for expression although I've heard others say they
had problems with heterogeneous termination. I'd try the standard
repertoire of techniques to improve expression. What has worked best
for me in the past were 1) lowering the temperature of
induction/expression and 2) using different tags.
It sounds like you've already tried many different parameters.
Consider different expression hosts.
ho
