T7 promoter 4

T7 promoter 4 is a variant of WT T7 promoter with reduced promoter strength. The T7 promoter has been shown to be modular, consisting of a 6 bp RNAP-binding region and a 5 bp strength determining region (Cheetham et al. 1999,Bandwar et al. 2002, Rong et al. 1998). Mutations to the strength-determining region alter promoter strength without affecting RNAP specificity (Davidson et al. 2010, Ikeda et al. 1992). Mutation of the strength-determining region from TAGGG to TAGGT results in a 4 fold reduced promoter strength compared to the wild type.