20世紀(jì)中期，Jensen發(fā)現(xiàn)有一種蛋白可以與人和兔血清抗體廣泛結(jié)合，該蛋白于1964年首次被稱(chēng)為Protein A。  Protein A是一種金黃色葡萄球菌細(xì)胞壁蛋白質(zhì)，分子量42KD，它能夠特異性地結(jié)合多種免疫球蛋白的Fc區(qū)段而與Fab區(qū)或輕鏈結(jié)合很弱。天然的Protein A有5個(gè)IgG結(jié)合結(jié)構(gòu)域和未知功能的非Fc結(jié)合域，結(jié)構(gòu)示意圖如下：

 此結(jié)構(gòu)的蛋白A大量結(jié)合IgG的同時(shí)，其非Fc結(jié)合域能結(jié)合部分雜蛋白，導(dǎo)致洗脫下來(lái)的IgG純度不夠，因此科學(xué)家利用基因工程的方法克隆Protein A的基因并進(jìn)行改造，得到重組型蛋白A，其非特異性結(jié)合明顯降低。重組的蛋白A經(jīng)過(guò)改造后有一個(gè)C端的半胱氨酸，可以單點(diǎn)偶聯(lián)到瓊脂糖上，降低空間位阻的同時(shí)提高IgG的結(jié)合能力。一步親和層析后樣品純度可超過(guò)90%。

蛋白Ｇ來(lái)自于鏈球菌Ｇ族的細(xì)胞表面蛋白，是III型Fc受體，分子量為25KD，其通過(guò)類(lèi)似于蛋白A的非免疫機(jī)制而結(jié)合抗體的Fc段，蛋白G與蛋白A均可結(jié)合抗體的Fc段，不同的是，蛋白G還能結(jié)合Fab段，且蛋白G可以更廣泛的結(jié)合更多類(lèi)型的IgG分子，多克隆IgG分子，同時(shí)蛋白G與血清蛋白結(jié)合水平低，產(chǎn)物純度高，且配基脫落更低?？贵w基本結(jié)構(gòu)和蛋白A/G的結(jié)合位點(diǎn)如下圖所示：

蛋白G可以純化不能與蛋白A結(jié)合的哺乳動(dòng)物抗體。重組型的蛋白G經(jīng)改造后已經(jīng)去除了白蛋白結(jié)合位點(diǎn)（血清白蛋白是抗體來(lái)源的主要污染物）及細(xì)胞表面結(jié)合位點(diǎn)，減少了非特異性結(jié)合。

相關(guān)資料：

MPB-vc-PAB-MMAE

MPB-MMAF

DBCO-PEG4-vc-PAB-MMAE

DBCO-PEG4-MMAF

DBCO-PEG4-Ahx-DM1

DBCO-PEG4-vc-PAB-Duocarmycin SA

DBCO-PEG4-vc-PAB-(PEG2)-Duocarmycin SA

DBCO-PEG4-VA-PBD

DBCO-PEG4-vc-PAB-MMAF

DBCO-PEG4-vc-PAB-MMAD

DBCO-PEG4-vc-PAB-Duocarmycin TM

DBCO-PEG4-vc-PAB-(PEG2)-Duocarmycin TM

DBCO-PEG4-vc-PAB-Duocarmycin DM

DBCO-PEG4-vc-PAB-(PEG2)-Duocarmycin DM

DBCO-PEG4-VC-PAB-DMAE-PNU159682

DBCO-PEG4-DMAE-PNU159682

DBCO-PEG4-GGFG-DX8951

DBCO-PEG4-vc-PAB-Ahx-DM1

DBCO-PEG8-VA-PAB-SG3199

Gly3-vc-PAB-MMAE

Gly3-MMAF

Gly5-Ahx-DM1

PNU159682-EDA-Gly3

ADC pre-screening kit A

Protein A-DM1

Protein A-MMAE

Protein A-MMAF

Protein A-Duocarmycin

Protein A-Calicheamicin

Protein A-PBD

ADC pre-screening kit G

Protein G-DM1

Protein G-MMAE

Protein G-MMAF

Protein G-Duocarmycin

Protein G-Amanitin

Protein G-Amanitin

Rabbit Anti-vc-PAB-MMAE pAb

Mouse Anti-vc-PAB-MMAE mAb (B11F11)

Rabbit Anti-MMAF pAb

Mouse Anti-MMAF mAb (F3B11)

Mouse Anti-MMAE / F mAb (B12A2)

Mouse Anti-MMAE /F mAb (C12A1)

Rabbit Anti-DM1/4 pAb

Mouse Anti-DM1/4 mAb (F1D5)

Mouse Anti-DM1/4 mAb (G2F3)

Rabbit Anti-Calicheamicin pAb

Mouse Anti-Calicheamicin mAb (B1G9)

Mouse Anti-Calicheamicin mAb (C1F12)

Rabbit Anti-Duocarmycin pAb 

Mouse Anti-Duocarmycin mAb (E11A1)

Mouse Anti-Duocarmycin mAb (H7A9)

Mouse Anti-Duocarmycin mAb (E6B3) 

Rabbit Anti-PNU-159682 pAb

Mouse Anti-PNU-159682 mAb (F7F2)

Mouse Anti-PNU-159682 mAb (C1E3)

Mouse Anti-PNU-159682 mAb (D12H11)

Rabbit Anti-Amanitin pAb

Mouse Anti-Amanitin mAb (H3E1)

Mouse Anti-Amanitin mAb (H12D6)

Mouse Anti-Amanitin mAb (C2C4)

Rabbit Anti-SN38 pAb

Mouse Anti-SN38 mAb (10F11A9D6)

Mouse Anti-SN38 mAb (8E10F12F3)

Mouse Anti-SN38 mAb (8E10A4A1)

Rabbit Anti-PBD SG3199 pAb

Mouse Anti-PBD SG3199 (7H6H9A6) mAb

Mouse Anti-PBD SG3199 (8G2H12A9) mAb

Mouse Anti-PBD SG3199 (8B3D12G1) mAb