HindIII site of the pET21b vector

With my recent experience as well as that I encountered when I was at NFRI in Japan, I would like to suggest you guys not to use the HindIII site at the multiple-cloning site of pET21b.

{mosgoogle}For a reason that is unclear to me at this time, this site is cut at a very low efficiency regardless whether you digest it sequencially or doubly.

Previously, I had great trouble digesting this vector at HindIII site. I was able to come to this conclusion when I cloned a fragment contains a HindIII site into the BamHI and SalI sites of pET21b and then digested the clone with BamHI and HindIII. The result showed that, while the HindIIII site within my insert was cute efficiently, the HindIII site of pET21b was poorly cut. This conclusion is based on only a single observation, your comments are almost welcome.