Question: The Gab operon is responsible for the conversion of γ-aminobutyrate to succinate, what is the  is the chief inhibitory neurotransmitter in the mammalian central nervous system, called?
Sentence (from "Gab operon"): There is a regulatory gene "csiR", downstream of the operon, that codes for a putative transcriptional repressor and is activated when nitrogen is limiting.
Relevant evidence: No