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sakura01_22木蟲 (小有名氣)
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[求助]
蛋白質(zhì)相互作用研究 蛋白A能pull-down蛋白B 反之檢測不出
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| 如題,在蛋白質(zhì)相互作用研究中,IP檢測,蛋白A能拉下蛋白B,但是蛋白B IP蛋白A時,檢測不出。重復(fù)3遍左右,依然檢測不出,希望哪位蟲友能幫忙解答一下。是否存在相互作用只能單方面pull-down的情況,這種情況如何解釋? |

專家顧問 (知名作家)
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專家經(jīng)驗: +218 |
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有人還是先去看看免疫共沉淀的實驗的原理吧!所要研究的可能存在相互作用的兩種蛋白質(zhì)——蛋白質(zhì)X和蛋白質(zhì)Y的彼此如果發(fā)生了相互作用是發(fā)生在細(xì)胞尚未裂解時!!而后是抗其中一個蛋白質(zhì)的單抗與其中一個蛋白質(zhì)發(fā)生免疫識別!這步能夠使蛋白質(zhì)變性嗎。??變性了還免疫識別個鬼呀!除非免疫簇就是序列免疫簇。序列免疫簇也是WB的實驗基礎(chǔ)原理之一,但是也是WB的局限性,WB不能檢測出空間抗原免疫簇因為熱煮沸和SDS變性而被破壞了的蛋白質(zhì)! 免疫共沉淀的實驗流程和簡圖如下: “The procedure for immunoprecipitation is outlined in Fig. 1. In the first step, cells are transfected with plasmids coding for a bait protein and its potential ligand, the target protein. These cells are lysed with a gentle detergenttreatment, creating a lysate containing bait–target complexes along with many irrelevant proteins. A capture antibody that specifically recognizes the bait protein is added to the lysates, forming a new antibody–bait–target complex. The antibody is then used as a handle to immobilize the proteins on inert Sepharose beads that are covalently coupled to Protein A, which stably binds the constant regions of many types of antibodies. At this point, those proteins not immobilized on beads are removed by a series of washes. Finally, the bait-protein complexes are eluted from the beads and dissociated by boiling in SDS. The presence or absence of the target protein, which is the endpoint of the assay, is evaluated by Western blot.” ——————From : Haian Fu edits ,Protein-Protein Interactions:Methods and Applications,Humana Press,2004,338. Haian Fu edits ,Protein-Protein Interactions:Methods and Applications,Humana Press,2004, http://www.gaoyang168.com/bbs/viewthread.php?tid=7764403 圖1.JPG |
木蟲 (著名寫手)
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可否用pull-down的方法嚴(yán)重一下b是否可以拉下a?你的那種情況我們組里面有人也出現(xiàn)過那種情況,后來用純化蛋白用pull down方法解決的,而不是用抗體。當(dāng)然,還有可能那兩蛋白不互作,有a拉b的假陽性。 蛋白互作能否用bifc方法來試試? [ 發(fā)自小木蟲客戶端 ] |
至尊木蟲 (知名作家)
Translator and Proofreader
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這種情況雖然少見,但卻是可以出現(xiàn)的。具體到你的情況: 1、確證用A之抗體Co-IP B的真實性,具體說要有對照(同種屬的control IgG對照)。 2、另選一種或幾種B的抗體試一試。許多抗體并非適于IP實驗,這時只能另選可能用的其他抗體。 3、用其他方法驗證A-B間的相互作用(physical interaction),如GST pulldown assays等。 4、可以用mammalian two-hybrid assay在功能上(functional interaction)研究A-B間的相互作用。 Good luck! |
木蟲 (小有名氣)

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