What is the role of catabolite activator protein (CAP) in LAC operon?

Catabolite activator protein, CAP is an activator required for high level transcription of the lac operon. CAP protein exes positive control and lac repressor exes negative control. What is an Operon? In prokaryotes, the genes coding for proteins involved in a paicular metabolic pathway are often sequentially arranged- together on the chromosome along with a single promoter or regulatory region. This entire cluster is termed as an operon, for eg, the lac operon (coding proteins for metabolism of lactose) or trp operon (coding proteins needed for the synthesis of tryptophan). Lac operon: Lac operon contains lacZ, lacY and lacA genes encoding beta galactosidase, galactose permease and thiogalactoside transacetylase and is preced by an operator (O) site and promoter (P) site. The operon is transcribed by RNA polymerase to produce a single polycistronic mRNA that is translated to produce all three enzymes which are involved in lactose metabolism.