 Polycystronic mRNA molecules formed in response to either promoter contain all the information required to synthesize the four Glector's enzymes. So, if a promoter has a transcription and the polycystronic mRNA is formed, it has complete information. Binding CAMPCRP to activator site repress transcription from P2 but activates transcription from P1. Moreover, P2 can support GEL mRNA transcription in the presence of glucose when intracellular CAMPCRP levels are low but P1 cannot do so. The fact that AS is 20 base pair closer to P1 in the GEL operon then it is in the LAC operon or promoter in the LAC operon leads one to predict that CAMPCRP and RNA polymerase interactions should be different in the GEL and LAC operons. Since you have seen the difference of 20 base pairs closer to P1 in the GEL operon, therefore it is expected that there will be a difference in the GEL operons. This prediction is correct. Cards like P1 in GEL operon that have AS at position minus 41.5 are called class 2 CAMP dependent promoter. Three activator regions on CRP that is AR1, AR2 and AR3 they interact with RNA polymerase hollow enzyme, AR1 on the upstream unit of the CRP dimer and AR2 and AR3 on the downstream subunit of dimer interact with alpha CTD or C-terminal domain, alpha NTD, alpha N-terminal domain and the sigma 70 subunit respectively. So here you can see this is polymerase hollow enzyme and its N-terminal domain alpha is CRP dimer and CRP dimer's downstream is AR1 then this is AR2 and its backside is AR3. So this is the RNA polymerase hollow enzyme. Why does the GEL operon has two promoters? The answer appears to be that galactose has two roles in the cellular metabolism. It is both a carbon source and a precursor for lipopolysaccharide synthesis. When galactose is not available in the growth medium cells require the epimerase specified by the GEL operon to convert glucose to galactose which is then used to make lipopolysaccharides. Synthesis from the P2 promoter permits the low level of epimerase formation required to convert glucose to galactose one phosphate so that the lipopolysaccharide can be formed. If P1 were the only promoter then epimerase could not be made when glucose is present because P1 requires CAMP-CRP activation. On the other hand if P2 were the only promoter then galactose could not be fully induced the operon when galactose was the sole carbon source because CAMP-CRP inhibits P2 thus for the sake of both necessity and economy a CAMP-CRP independent promoter which is P2 is needed for background constitutive synthesis and a CAMP-CRP dependent promoter P1 is needed to regulate high level synthesis so P1 and P2 are required furthermore the regulation is efficient only if P2 is inhibited by CAMP-CRP.