The pET-11a-d vectors carry an N-terminal T7•Tag® sequence and BamH I cloning site. Thesevectors are the precursors to many pET family vectors; the pET-21a-d(+) series corresponds topET-11a-d but incorporates several additional features. Unique sites are shown on the circle map.Note that the sequence is numbered by the pBR322 convention, so the T7 expression region isreversed on the circular map. The cloning/expression region of the coding strand transcribed byT7 RNA polymerase is shown below.