DH5-Alpha Cell

DH5-Alpha Cells are E. coli cells engineered by American biologist Douglas Hanahan to maximize transformation efficiency. They are defined by three[1] mutations: recA1, endA1 which help plasmid insertion and lacZΔM15 which enables blue white screening. The cells are competent and often used with calcium chloride transformation to insert the desired plasmid. A study of four transformation methods and six bacteria strains showed that the most efficient one was the DH5 strain with the Hanahan method.[2]

Mutations
  • The recA1 mutation is a single point mutation that replaces glycine 160 of the recA polypeptide with an aspartic acid residue[3] in order to disable the activity of the recombinases and inactivate homologous recombination.
  • The endA1 mutation inactivates an intracellular endonuclease to prevent it from degrading the inserted plasmid.[4]

References
  1. Wertz J. "Strain - DH5α". The Coli Genetic Stock Center (CGSC). Yale University. Retrieved 2017-05-23.
  2. Chan WT, Verma CS, Lane DP, Gan SK (December 2013). "A comparison and optimization of methods and factors affecting the transformation of Escherichia coli". Bioscience Reports. 33 (6). doi:10.1042/BSR20130098. PMC 3860579. PMID 24229075.
  3. Bryant FR (June 1988). "Construction of a recombinase-deficient mutant recA protein that retains single-stranded DNA-dependent ATPase activity" (PDF). The Journal of Biological Chemistry. 263 (18): 8716–8723. doi:10.1016/S0021-9258(18)68364-4. PMID 2967815.
  4. Taylor RG, Walker DC, McInnes RR (April 1993). "E. coli host strains significantly affect the quality of small scale plasmid DNA preparations used for sequencing". Nucleic Acids Research. 21 (7): 1677–1678. doi:10.1093/nar/21.7.1677. PMC 309390. PMID 8479929.
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