pET-30a質(zhì)粒是一種原核表達(dá)載體，C端含有一個(gè)6×His affinity標(biāo)簽，N端含有一個(gè)thrombin位點(diǎn)、6×His affinity標(biāo)簽、EK標(biāo)簽和S標(biāo)簽。該質(zhì)粒含有多個(gè)常用的酶切位點(diǎn)，便于不同基因克隆。表達(dá)由宿主細(xì)胞提供的T7 RNA聚合酶誘導(dǎo)，目的基因被克隆到質(zhì)粒載體上，受噬菌體強(qiáng)轉(zhuǎn)錄及翻譯信號(hào)控制。
pET系統(tǒng)是有史以來在大腸桿菌中表達(dá)重組蛋白的功能*強(qiáng)大的系統(tǒng)，也是現(xiàn)今原核表達(dá)方面使用*廣泛的系統(tǒng)。該系列質(zhì)粒能很容易的通過降低誘導(dǎo)物的濃度來削弱蛋白表達(dá)。在非誘導(dǎo)條件下，可以使目的基因處于完全沉默狀態(tài)而不轉(zhuǎn)錄。
The pET-30a-c(+) vectors carry an N-terminal His? Tag®/ thrombin/ S? Tag?/ enterokinase configuration plus an optional C-terminal His? Tag sequence. Unique sites are shown on the circle map. Note that the sequence is numbered by the pBR322 convention, so the T7 expression region is reversed on the circular map. The cloning/expression region of the coding strand transcribed by T7 RNA polymerase is shown below. The f1 origin is oriented so that infection with helper phage will produce virions containing single-stranded DNA that corresponds to the coding strand. Therefore, single-stranded sequencing should be performed using the T7 terminator primer .