Can I use the white-blue system to screen a yeast cDNA library without disrupting the cells. Is it possible to apply the Xgal directly in the growth medium?
We want to select for events in which the interaction is disrupted (=counter selection) - wondered if we could use the white-blue scheme and avoid using toxic and expensive 5FOA (and to avoid replicating the colonies)...
Practically, you cannot.
Beta-galactosidease is not secreted out of yeast cells, and X-gal does not enter the yeast cells efficiently. So, the enzyme and the substrate will not meet with each other.
Also, beta-galactosidase requires K+ ion, Mg2+ ion and beta-mercaptoethanol. I don't if yeast cells are happy with them.
If your Y2H strain has the MEL1 reporter gene, you can use X-alpha-Gal.
MEL1 encodes a secreted alpha-galactosidase, and X-alpha-Gal is a substrate for the enzyme. The combination will allow you direct blue-white screening of colonies.
However, X-alpha-Gal is quite expensive.
So you will need to consider about the cost of screening.
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