Gene Regulation and Transcriptional Regulation in Bacteria
The catabolite gene activator protein (CAP) and the fumurate nitrate reductase (FNR) are two founder members of the growing CRP-FNR protein superfamily. The consensus FNR binding site (TTGAT-N4-ATCAA) closely resembles that of CRP to the extent that both contain a common core motif (NTGAN-N4-NTCAN). The transcription factor FNR plays a role in altering gene expression between aerobic and anaerobic conditions but CRP regulators control the response to glucose starvation. Protein DNA interactions occur between the regulatory protein and DNA at the corresponding promoter using the consensus either CRP or FNR binding sites. Successful transcriptional activation generally requires contact between a DNA-bound activator and RNA polymerase in order to generate on effective complex. CRP promoters are grouped into two classes depending on the location of DNA binding site. Class I promoters contains transcription activator binding sites centered near position -61.5, -71, -82 or -92. Class II promoters the regulator proteins bind to a site centered at or near -41.5 so three possible contacts, αCTD-AR1, αNTD-AR2 and δ70-AR3, occur between regulator and RNA polymerase. FNR and FLP act as a class II activator.
Key Words: Transcription regulation, FNR, CAP, FLP.