what is the strongest protein-protein interaction?

shifali chatrath via methods%40net.bio.net (by shifalich from rediffmail.com)
Sun Nov 16 22:48:19 EST 2008

Avidin-Biotin interation is strongest known interaction till date. It has affinity constant of femtomolar range, followed by antigen antibody interaction which is of picomolar range on an average.
You can try tagging protein A with Biotin and B with Avidin.It wont interfere with protein function if yours are plant proteins. Biotin is Vit.B2.
hope it helps. 

On Sat, 15 Nov 2008 Zhong Silin wrote :
>Hi all
>I want to find a method to pulldown a target protein A indirectly. (it just has to be indirect)
>I am thinking: to express protein A with epitope tag x first (A-x), then express a second protein B with another epitope tag y (B-y). Protein B will interact with tag x and Protein A can then be co-purified using the epitope tag y, which is fused to protein B.
>For tag x and protein B, I only got 2 pairs of candidates: IgG and protein A/G; N- and C-terminal of the fluorescent protein. Or use the biotin ligase as protein B and fuse the recognition sequence to protein A as tag x.
>The ideal tag x and protein B also have to be small so they wont interfere with the function of protein A. Their interaction has to be strong as well.
>I worked on plants and I know our techniques are always a bit behind animal sciences. So you guys must have a better systems to do this. But please keep in mind that this method has to be two-step and indirect!
>Thanks in advance
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Shifali Chatrath
Graduate Student
Protein science Lab
Dept. of Biological sciences
National University of Singapore

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