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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.
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 dr...
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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 (Nalr), thi-1, hsdR17 (rk–, mk+), e14– (McrA–), relA1, supE44, Δ(lac-proAB), Δ(rhaBAD)::T7 RNA polymerase.
For more information, see the Protocols & Applications Guide.
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Single Step (KRX) Competent Cells
Always store competent cells at –70°C. Thaw on ice when ready for use. Do not refreeze thawed, unused aliquots.
For product intended use please see Patents & Disclaimers tab.
This one strain consolidates the best attributes of both good cloning and good expression strains avoiding the need to transfer to another strain specifically for expression.
Lane 1, BL21(DE3); lane 2, BL21(DE3)pLysS; lane 3, Rosetta 2(DE3) pLysS; lane 4, Single Step (KRX) Competent Cells.
L3002, L5701, L5702 For Research Use Only. Not for Use in Diagnostic Procedures.
L3002 Patent Pending.
L3002 Usage Restrictions for the T7 Expression System
The T7 expression system is based on technology developed at Brookhaven National Laboratory under contract with the U.S. Department of Energy and is the subject of patents assigned to Brookhaven Science Associates, LLC (BSA). This technology, including bacteria, phage and plasmids that carry the gene for T7 RNA polymerase, is to be used for academic or nonprofit laboratory or licensed commercial research purposes only. By accepting or using the T7 expression technology you agree to be bound by the following conditions set forth by BSA. The initial purchaser may refuse to accept the conditions of this notice by returning this product and the enclosed materials to Promega unused.
Academic and NonProfit Laboratories
No materials that contain the cloned gene for T7 RNA polymerase may be distributed further to third parties outside of your laboratory unless the recipient receives a copy of this assurance notice and agrees to be bound by its terms. This limitation applies to Bacterial Strains JM109(DE3), BL21(DE3)pLysS and KRX and to any derivatives thereof.
A license is required for any commercial use of the T7 expression system, including use of the T7 system for research purposes or for production purposes by any commercial entity. Information about commercial licenses may be obtained from the Licensing Office, Brookhaven National Laboratory, Upton, NY 11973, Telephone: 631-344-7134, FAX: 631-344-3729.
L3002 Usage restrictions apply to Bacterial Strains JM109(DE3), BL21(DE3)pLysS and KRX and to any derivatives thereof.
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