myTXTL supports all promoters used in E. coli protein expression, including promoters that rely on the endogenous E. coli transcription machinery and those that require a separate RNA polymerase such as T7. All kits come with a Helper plasmid to express the T7 RNA polymerase and enable transcription from T7 promoters. If a promoter is used that is recognized by the E. coli RNA polymerase, then this helper plasmid is not needed. If using a plasmid with an inducible promoter, such as the pET vectors, you need to add your inducer IPTG at 1 mM to the reaction and you may want to explore plasmid concentration in the range of y your inducer like IPTG if it is an inducible promoter.