各種感受態(tài)細(xì)胞的區(qū)別、用途和特征
Xl1-Blue菌株
基因型：endA1 gyrA96(nalR) thi-1 recA1 relA1 lac glnV44 F‘[Tn10 proAB+ lacIq Δ(lacZ)M15] hsdR17(rK- mK+)。
特點：具有卡那抗性、四環(huán)素抗性和氯霉素抗性。 用途：分子克隆和質(zhì)粒提取。
BL21(DE3)菌株
基因型：F– ompT gal dcm lon hsdSB(rB- mB-) λ(DE3 [lacI lacUV5-T7 gene 1 ind1 sam7 nin5])。
特點：該菌株用于以T7 RNA聚合酶為表達(dá)系統(tǒng)的外源基因的蛋白表達(dá)宿主。T7噬菌體RNA聚合酶基因的表達(dá)受控于λ噬菌體DE3區(qū)的lacUV5啟動子，該區(qū)整合于BL21的染色體上。該菌適合于非毒性蛋白的表達(dá)。
用途：蛋白質(zhì)表達(dá)。
BL21(DE3)ply菌株
基因型：F- ompT gal dcm lon hsdSB(rB- mB-) λ(DE3) pLysS(cmR)。
特點：該菌株帶有pLysS，具有氯霉素抗性。此質(zhì)粒還有表達(dá)T7溶菌酶的基因，T7溶菌酶能夠降低目的基因的背景表達(dá)水平，但不干擾IPTG誘導(dǎo)的表達(dá)。 適合于毒性蛋白和非毒性蛋白的表達(dá)。 用途：蛋白質(zhì)表達(dá)
Competent E. coli
Full Product Description BL21 Star™ E. coli strains are high-performance BL21 hosts designed for improving protein yield in a T7 promoter-based expression system. Because T7 RNA polymerase synthesizes mRNA more rapidly than E. coli RNA polymerases, transcription from the T7 promoter is uncoupled to translation in E. coli. This results in mRNA transcripts unprotected by ribosomes, which are then subject to enzymatic degradation by endogenous RNases (1). The reduced level of transcripts in the cell often leads to greatly reduced levels of protein yield (Figure1). The BL21 Star™ strains contain a mutation in the gene encoding RNaseE (rne131), which is one of the major sources of this mRNA degradation (2). BL21 Star™ cells significantly improve the stability of mRNA transcripts and increase protein expression yield from T7 promoter-based vectors (3) (Figure 2).
BL21 Star™(DE3) is ideal for expressing proteins that are non-toxic to E. coli.
BL21 Star™(DE3)pLysS offers lower basal-level expression of heterologous genes than BL21 Star™(DE3). It is designed for expressing proteins that are slightly growth inhibitive to E. coli.

DH5α菌株
基因型：F- endA1 glnV44 thi-1 recA1 relA1 gyrA96 deoR nupG Φ80dlacZΔM15 Δ(lacZYA-argF)U169, hsdR17(rK-, λ–
特點：一種常用于質(zhì)?？寺〉木?。 其Φ80dlacZΔM15基因的表達(dá)產(chǎn)物與pUC載體編碼的β-半乳糖苷酶氨基端實現(xiàn)α互補(bǔ)，可用于藍(lán)白斑篩選。recA1和 endA1的突變有利于克隆DNA的穩(wěn)定和高純度質(zhì)粒DNA的提取。
用途：分子克隆、質(zhì)粒提取和蛋白質(zhì)表達(dá)
JM109菌株
基因型：endA1 glnV44 thi-1 relA1 gyrA96 recA1 mcrB+ Δ(lac-proAB) e14- [F‘ traD36 proAB+ lacIq lacZΔM15]hsdR17(rK-mK+)。
特點：部分抗性缺陷，適合重復(fù)基因表達(dá), 可用于M13克隆序列測定和藍(lán)白斑篩選。 用途：分子克隆、質(zhì)粒提取和蛋白質(zhì)表達(dá)。

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