Question

A gene regulatory protein called ArgP regulates the transcription of enzymes for arginine biosynthesis in the bacterium E.coli. ArgP is an allosteric protein whose activity is modulated by arginine. Upon binding arginine, ArgP alters its conformation and binds more tightly to the regulatory sequence in the promoters of the genes for the arginine biosynthetic enzymes.

Does ArgP function as a gene activator or repressor? Explain your answer.

Answer 1

ArgP is a transcriptional regulator of arginine biosynthesis. ArgP - Arg interaction followed by binding to the promotor region activates the transcription of Arg synthesis. However, presence of lysineconverts ArgP to a repressor. Since the binding to Arg makes ArgP binding to the promotor stronger due to conformational changes, leading to further bending of DNA followed by stronger transcription by RNA polymerase gene in Ecoli strain would make it apt to be called an activator.