How do I prepare an insert for pQE vectors?
FAQ ID -185

In general, it is only necessary to prepare the insert by restriction digestion and gel purification. The fragment can be ligated into the vector directly. If there is no appropriate restriction site, if it is desirable to minimize the number of extra codons, or if the construct must be optimized in some other way, more complicated manipulations may be necessary. The ends of coding fragments can be modified by PCR, by in vitro mutagenesis, or by the addition of linkers. Please refer to standard laboratory manuals for details on such procedures.

If the 6xHis tag needs to be integrated into other vectors, please follow the recommendations in the 'Cloning' chapter of the QIAexpressionist handbook, section "Integration of 6xHis tags in other vectors".