PIR2 ONESHOT CHEN 10 RXN，C111110，Invitrogen

The Echo™ Cloning System is a two-vector system that utilizes the Cre-lox site-specific recombination system of bacteriophage P1 (1,2) for rapid cloning into multiple vectors. Your gene of interest is cloned into one of the specially designed donor vectors which can then be recombined with as many different Echo™ acceptor vectors as desired. The donor and acceptor vectors are placed in a buffer that contains Cre recombinase for a 25-minute, in vitro recombination reaction. Cre binds to the lox site present on each vector, brings them together, then cleaves and covalently reattaches the DNA strands. The end result is a fusion of the donor and acceptor vectors forming a single, functional expression vector.
PIR2 competent cells are recommended for maintaining constructs that express toxic genes or for libraries. Use them for cloning and maintenance of your donor vector construct (or other vector containing the R6K? origin). It contains the wild-type pir gene
for maintenance of the vector at ~15 copies per cell.