Hi there,

I don't know whether there's a good antibody available for your protein of interest, if so: what about doing an IP with a good antibody and going for mass spec to identify interaction partners? To start, you could make a small database that consists of all the different isoforms of calmodulin to have it checked with the mass spec raw files and try to get a first hint.

Dear Richard,

Simple size-exclusion can show you protein binding by complex formation or shift of your proteins to higher masses. An alternative is protein cross-link with glutardehyde, for this purpose you need to set up the cross-linker and protein concentration not to overdo. If you will observe any kind of interaction after EDTA addition it will mean not-specific binding of the proteins. Since multimers of calmodulin are known, the controls of single proteins in both techniques are essential. The well planed experiment on recombinant proteins can give you a clue about the strenght of the interaction.

Keep fingers cross - Jan

How many different calmodulins do you have?

You could perform MicroScale Thermophoresis (MST) experiments. This would also allow to not only obtain information IF your protein binds a certain calmodulin, but also which affinity they are binding to. So you could see if one calmodulin-like protein is binding stronger compared to a different one.

These experiments can also be done with Ca2+ or in the presence of EDTA.

http://www.nanotemper-technologies.com/applications/

Depends if you want to know exact affinities or just a general survey of the binding partners. For the former, ITC experiments are probably your best bet. For the latter, you could try a yeast two hybrid screen.