pET vector problems

[John Brennand, Tel 4639/5739/6636]

We have experienced some problems with commercially available pET vectors. We 
noted that pET21 but not pET11 had a mutation in the lacI gene that would lead 
to an inability to form tetramers.  This may interfere with expression control 
and hence lead to problems with toxic products.

The moral is - sequence the vectors yourself.