The pET-19b vector (Cat. No. 69677-3) carries an N-terminal His?Tag? sequence followed by an enterokinase site and three cloning sites. Unique sites are shown on the circle map. Note that the sequence is numbered by the pBR322 convention, so the T7 expression region is reversed on the circular map. The cloning/expression region of the coding strand transcribed by T7 RNA polymeraseis shown below.