MC1061/P3 Chemically Competent E. coli are used for highly efficient transformations that require the P3 episome for selection and maintenance of vectors encoding the tyrosine tRNA suppressor (synthetic supF gene, such as pCDM8, pcDNA1.1, or any other supF-containing vector).

MC1061 E. coli cells were used by Hanahan and coworkers to engineer the DH10B strain. Among the replaced genes by adding mutations were recA1 (inhibiting the homologous recombination system), endA1, and lacZΔM15. Thus, this strain with its intact homologous recombination system is used in applications where recombination is needed, such as in genetically engineering E. coli by recombination or plasmid-phage recombination.

MC1061/P3 Chemically Competent E. coli offer:
• Transformation efficiencies of >1 x 10⁸ cfu/μg
• P3 plasmid for selection of supF-containing plasmids
• hsdR for efficient transformation of unmethylated DNA from PCR amplifications

P3 plasmid
The P3 plasmid is a low-copy-number, 60 kb plasmid that carries kanamycin, tetracycline, and ampicillin resistance markers. The kanamycin gene is fully active and used to select for cells carrying P3. The tetracycline and ampicillin genes carry amber mutations, which render the genes inactive during normal growth and replication of the bacteria. Upon transformation of a vector carrying the suppressor F gene, the amber mutations in the tetracycline and ampicillin genes on the P3 plasmid are suppressed, and the E. coli are resistant to these antibiotics.

Note: The spontaneous reversion rate for the amber mutation in the ampicillin marker is 5%, while the reversion rate for the amber mutation in the tetracycline marker is 1%.To minimizing the reversion rates, use tetracycline and ampicillin together for selection of E. coli (P3) cells transformed with the SupF plasmid.

Genotype
F^–hsdR(r_K–, m_K+) araD139 Δ(araABC-leu)7679 galU galK ΔlacX74 rpsL(StrR) thi mcrB / P3: Kan^R Amp^R (am) Tet^R (am)

Find the strain and format that fits your needs
We offer DH strains in chemically competent and electrocompetent cell formats to meet your specific needs.
The TOP10/P3 strain could be used where recombination is not needed.
Strains are available in several MultiShot formats for high throughput applications.
Explore bacterial growth media formats.