EXPRESSYS - pZ Host Strains

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"Zi" strains carry at their attB locus two copies of the laci^q gene encoding the Lac Repressor. "Z1" strains carry at their attB locus two copies of Lac Repressor and Tet Repressor encoding genes (laci and tetR, respectively) driven by the constitutive promoters P_laciq and P_N25, respectively. The genes encoding the regulatory proteins are accompanied by a gene conferring resistance to Spectinomycin (Sp^R). Transfer of the regulatory module to other strains can be accomplished via general transduction, e.g. by phage P1.

Strain	Genotype	Main Features

DH5alphaZi	laci^q, Sp^R, deoR, supE44, Delta(lacZYA-argFV169), Phi80 lacZDeltaM15, hsdR17(rK- mK+), recA1, endA1, gyrA96, thi-1, relA1	Its high transformation efficiency makes DH5alpha suited for DNA cloning and DNA preparation. Due to its relatively low growth rates it is not widely used for large scale protein production (e.g. by fermentation)
DH5alphaZ1	laci^q, PN25-tetR, Sp^R, deoR, supE44, Delta(lacZYA-argFV169), Phi80 lacZDeltaM15, hsdR17(rK- mK+), recA1, endA1, gyrA96, thi-1, relA1	see DH5alphaZi
C600Zi	laci^q, Sp^R, lacY1, leuB6,mcrB+, supE44, thi-1, thr-1, tonA21	A high transformation efficiency combined with extremly fast growth rates makes C600Z1 a superb candidate for DNA cloning as well as high level protein production. RecA mediated chromosomal integration of DNA-sequences and general transduction, e.g. by P1, is also feasible.
C600Z1	laci^q, PN25-tetR, Sp^R, lacY1, leuB6,mcrB+, supE44, thi-1, thr-1, tonA21	see C600Zi
W3110Z1	laci^q, PN25-tetR, Sp^R, IN (rrnD-rrnE)1, rph-1 (see: ATCC 39936)	W3110 is widely used in large scale protein production processes (fermentation). Due to its low transformation efficiency it is not well suited for DNA cloning.

Nomenclature and Abbreviations

largFV169: Inability to utilize arginine; ornithine carbamoyltransferase mutation

deoR: Allows uptake of large plasmids; regulatory gene mutation allowing constitutive expression of genes for deoxyribose synthesis

endA1: Abolishes non-specific endonuclease I activity; improves quality of plasmid DNA isolations

gyrA96: Resistance to nalidixid acid; DNA gyrase mutation

hsdR17(rK- mK+): Restriction minus, modification positive; transformed DNA will not be cleaved by endogeneous restriction endonucleases

acY1: Galactoside permease mutation; inability to use lactose,

laci^q: lac promoter up-mutation; constitutive overproduction of Lac repressor

leuB6: beta-isopropyl malate dehydrogenase mutation; requires leucin for growth on minimal media

lacZmcrB+: Blocks restriction of methyl-cytosin-specific DNA sequences

DeltaM15: Allows a-complementation of b-galactosidase activity, partial deletion of beta-D-galactosidase gene

PN25-tetR: constitutive production of Tet repressor

recA1: Prevents recombination between introduced DNA and host DNA; confers UV-light sensitivity

relA1: Allows RNA synthesis in the absence of protein synthesis

Sp^r: resistance to Spectinomycin

supE44: Suppresses amber (UAG) mutations

thi-1: Requires thiamine for growth on minimal media

thr-1: Requires threonine for growth on minimal media

tonA21: Mutation in outer membrane protein; resistance to bacteriophage T1

References

C600: Huynh, T. V. et al. (1985) In: DNA Cloning, Ed. Glover, D. M. (IRL Press Ltd., Oxford, England), vol. 1, 49-110.

DH5alpha: Hanahan, D. (1983) J. Mol. Biol., 166, 557-580.

W3110: Bachmann, B. J. (1972) Bacteriol. Rev., 36, 525-530.