#Dna binding repertoire biology meaning code#

Once isolated, the proteins were shown to bind to specific DNA sequences close to the genes that they regulate. They were eventually purified by fractionating cell extracts. Because these proteins, like most gene regulatory proteins, are present in small quantities, it was difficult and time-consuming to isolate them. It was proposed at the time, and later proven, that most of these mutants were deficient in proteins acting as specific repressors for these sets of genes. The first step toward understanding gene regulation was the isolation of mutant strains of bacteria and bacteriophage lambda that were unable to shut off specific sets of genes. The lac repressor, the first of these bacterial proteins to be recognized, turns off the production of the proteins responsible for lactose metabolism when this sugar is absent from the medium. Other bacterial regulators respond to nutritional conditions by shutting off genes encoding specific sets of metabolic enzymes when they are not needed.

The lambda repressor was among the first gene regulatory proteins to be characterized, and it remains one of the best understood, as we discuss later.

#Dna binding repertoire biology meaning code#

The repressor shuts off the viral genes that code for the protein components of new virus particles and thereby enables the viral genome to remain a silent passenger in the bacterial chromosome, multiplying with the bacterium when conditions are favorable for bacterial growth (see Figure 5-81). One of these regulators, the lambda repressor, is encoded by a bacterial virus, bacteriophage lambda. Genetic analyses in bacteria carried out in the 1950s provided the first evidence for the existence of gene regulatory proteins that turn specific sets of genes on or off. Gene Regulatory Proteins Were Discovered Using Bacterial Genetics