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Abstract for Single Step (KRX) Competent Cells
Single Step (KRX) Competent Cells are prepared from the KRX
strain, which is an E. coli K12 derivative that has salient
features associated with cloning and screening strains plus
engineered attributes to optimize controlled protein expression.
Attributes that make this a good cloning strain are the partially
defective restriction systems (hsd and e14), a lack of the most
common nuclease that copurifies with plasmid DNA isolated from E.
coli strains (endA), and a preventive mutation to
minimize undesirable recombination events (recA). KRX can
also be used for blue/white screening, because it is deficient in β-galactosidase
activity due to deletions in both genomic and episomal copies of the
lacZ gene. The partial deletion in the episomal (F´factor) copy of
the lacZ gene (Δ(lacZ)M15) can be complemented by the
addition of a functional α-peptide encoded by a plasmid cloning
vector. KRX also has attributes that make it a good protein
expression strain. The ompT and ompP mutations eliminate one source
of proteolysis of
overexpressed protein in E. coli.
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