RecA
From Wikipedia, the free encyclopedia
recA is a 38 kilodalton Escherichia coli protein essential for the repair and maintenance of DNA. RecA has a structural and functional homolog in every species in which it has been seriously sought and serves as an archetype for this class of homologous DNA repair proteins. The homologous protein in Homo sapiens is called RAD51.
RecA has multiple activities, all related to DNA repair. In the bacterial SOS response, it has a co-protease function in the autocatalytic cleavage of the LexA repressor and the λ repressor. Its most studied role is in facilitating DNA recombination for the repair of double strand DNA breaks and the exchange of genetic information through sexual reproduction.
E.Coli strains deficient in recA are useful for cloning procedures in molecular biology laboratories. Escherichia coli strains are often genetically modified to contain a mutant recA locus to ensure the stability of exogenous plasmids: modular circular dsDNA which bacteria replicate with their genome during normal cell growth. Plasmid DNA is taken up by the bacteria under a variety of conditions. Bacteria containing exogenous plasmids are called "transformants". Transformants retain the plasmid throughout cell divisions. such that it can be recovered and used in other applications. Without functional recA protein the exogenous plasmid DNA is left unaltered by the bacteria. Purification of this plasmid from bacterial cultures then results in high-fidelity amplification of the original plasmid sequence.
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