Question

What does the lac repressor protein from bacteria have in common with the Gal4 protein from yeast?

Answer 1

Thus in simple terms both the lac repressor protein from bacteria and Gal4 protein from yeast both act as repressor when considering the bacterial cell. The lac repressor operator system can be replaced functionally by a eukaryotic DNA-binding protein and its DNA recognition site. the gal4 protein made in E.coli acquires a conformation that permits rather specific DNA
recognition on the chromosome of E. coli. Even though in yeast this protein is a positive transcription activator, in E. coli under
these circumstances it can act as a repressor.
Here the binding of a gal4 protein dimer to the target DNA that overlaps the transcription initiation site will inhibit transcription
by a mechanism similar to that of the lac repressor.The gal4 protein is high enough to achieve a repression rate of at least
30-fold after the induction of gal4 synthesis. The inhibition of bacterial growth after induction suggests that other sequences on the chromosome may be recognized by the
gal4 protein, which thereby interferes with the expression of one or more essential bacterial genes.