Number of promoters and length of promoter core sequence

Range ~3,000 promoters: each containing a core sequence of ~35 base pairs (bp)
Organism Bacteria Escherichia coli
Reference Wang F, Redding S, Finkelstein IJ, Gorman J, Reichman DR, Greene EC. The promoter-search mechanism of Escherichia coli RNA polymerase is dominated by three-dimensional diffusion. Nat Struct Mol Biol. 2013 Feb20(2):174-81. doi: 10.1038/nsmb.2472 p.174 left column bottom paragraphPubMed ID23262491
Primary Source See link
Comments P.174 left column bottom paragraph: "Escherichia coli has ~3,000 promoters, each containing a core sequence of ~35 base pairs (bp) in length, with hexameric consensus sites at the −35 (TTGACA) and −10 (TATAAT) regions [primary sources]. Prior to synthesizing a transcript, RNAP must find appropriate promoter sequences. Like all DNA-binding proteins, RNAP is expected to employ some form of diffusion to locate its targets (Supplementary Fig. 1)[ref 7]."
Entered by Uri M
ID 113765