* Promoter - commonly used inducible promoters are promoters derived from lac operon and the T7 promoter. Other strong promoters used include Trp promoter and Tac-Promoter, which are a hybrid of both the Trp and Lac Operon promoters. 
* Ribosome binding site (RBS) - follows the promoter, and promotes efficient translation of the protein of interest. 
* Translation initiation site - Shine-Dalgarno sequence enclosed in the RBS, 8 base-pairs upstream of the AUG start codon.