Galactose concentrations?

Robert Randolph rand777 at
Tue Aug 13 08:01:41 EST 1996

On Mon, 12 Aug 96 15:29:06 PST, Email (YourName) wrote:

>Hi there. I want to screen an inducible Arabidopsis cDNA library in yeast.
>Looking through the literature, the promoter (GAL4) is induced in liquid
>culture lacking glucose with 1% galactose. Does anybody have any experience
>in reducing this galactose concentration. How low can I go before the
>promoter is turned off? and what conc of glucose will turn off 
>the promoter?? Thanks.

My experience has shown that any glucose present at any concentration
will be utilized.  I would suggest a broth containing 100 mg/l
glucose and 5 gm galactose to induce the promoter.  The glucose will
yield active log growth and will accelerate the conversion.  If one
adds a small amount of glucose back into the system (50 mg./l) the
promoter will be momentarily arrested and then "restart" when the
available glucose is metabolized. RR

Robert Randolph
Randolph Biomedical
rrandy at

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