C41(DE3) and C43(DE3) strains derived of BL21(DE3) strain E.coli. I am searching for where the mutated genes are in C41 and C43 strains and also the function of these genes in the wild type BL21 strain.
Essentially, they have mutations in the lacUV5 promoter that drives expression of T7 RNA Pol. There is a detailed analysis at Wagner, S., Klepsch,et al. Tuning Escherichia coli for membrane protein overexpression. Proc.Natl.Acad.Sci.U.S.A 105(38), 14371-14376 (PMID 18796603)