Interviewee: Walter Gilbert. Walter Gilbert talks about identifying the lac operon repressor. (DNAi Location: Code > Controlling the code > Players > Walter Gilbert > The lac operon repressor)

I and Benno Muller-Hill, who was at that time a post-doc with me, started to work on that problem involving the repressor for the lactose operon, and on a set of genes involving the metabolism of the sugar lactose. We worked on it because we knew it was a fundamental problem in biology, and the problem that we were attacking was what is the nature of the product made by one gene that turns off a second one. The answer in those days that we came to was the product is a protein that goes and binds to DNA and prevents a second gene from functioning. The small molecule of sugar coming into the cell, inactivates that protein, makes it release its hold on DNA and then the genes begin to function. There are only ten molecules of that protein in a bacterial cell, it was extremely hard to identify, and we did a set of experiments in the middle Sixties that actually enabled us to identify that protein, it was the first control protein identified.

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