GAL2

GAL2 is a gene found in the yeast Saccharomyces cerevisiae. It encodes a protein that is a component of the GAL4 transcriptional activator system. This system is crucial for the yeast's ability to metabolize galactose. When galactose is present in the environment, the GAL4 protein binds to specific DNA sequences, known as upstream activating sequences (UAS), located in the promoter regions of genes involved in galactose metabolism. This binding event initiates transcription of these genes, allowing the yeast to utilize galactose as an energy source.

The GAL2 protein specifically functions as a galactose permease. Permeases are transport proteins embedded in the cell membrane that facilitate the movement of specific molecules across the membrane. The GAL2 permease is responsible for transporting galactose from the extracellular environment into the yeast cell. Without a functional GAL2 permease, even if the transcriptional machinery is activated by GAL4, galactose cannot enter the cell to be metabolized. Therefore, GAL2 is an essential gene for galactose utilization in S. cerevisiae. Mutations in GAL2 typically result in the inability of the yeast to grow on galactose as the sole carbon source. The regulation of GAL2 expression is tightly controlled by the presence or absence of galactose and glucose.