The Single Step (KRX) Competent Cells are designed for efficient transformation and tightly controlled protein expression. These cells consolidate the best attributes of these two steps into one strain to evaluate protein expression in E. coli. In two days, you can transform your vector into the Single Step (KRX) Competent Cells and be ready for protein expression. Transformation efficiencies are greater than 10⁸ cfu/μg, similar to other highly competent cells. The single step cells are available in single transformation size (50μl). KRX also can be used for blue/white screening. Single Step (KRX) is an E. coli K strain that contains a chromosomal copy of the T7 RNA polymerase driven by a rhamnose promoter (rhaBAD) to provide dramatic control of the proteins expressed via a T7 promoter. Pre-induced expression protein levels are significantly lower than those of BL21(DE3)-derived strains. This feature facilitates cloning and expression of proteins toxic to E. coli.

Genotype: [F´, traD36, ΔompP, proA⁺B⁺, lacIq, Δ(lacZ)M15] ΔompT, endA1, recA1, gyrA96 (Nal^r), thi-1, hsdR17 (r_k^–, m_k⁺), e14^– (McrA^–), relA1, supE44, Δ(lac–proAB), Δ(rhaBAD)::T7 RNA polymerase.