In bacteria, the promoter contains two short sequence elements approximately 10 (Pribnow Box) and 35 nucleotides upstream from the transcription start site.
* The sequence at -10 (the -10 element) has the consensus sequence TATAAT.
* The sequence at -35 (the -35 element) has the consensus sequence TTGACA.
* The above consensus sequences, while conserved on average, are not found intact in most promoters. On average, only 3 to 4 of the 6 base pairs in each consensus sequence are found in any given promoter. Few natural promoters have been identified to date that possess intact consensus sequences at both the -10 and -35; artificial promoters with complete conservation of the -10 and -35 elements have been found to transcribe at lower frequencies than those with a few mismatches with the consensus.
* The optimal spacing between the -35 and -10 sequences is 17 bp.
* Some promoters contain one or more upstream promoter element (UP element) subsites (consensus sequence 5-AAAAAARNR-3 when centered in the -42 region; consensus sequence 5-AWWWWWTTTTT-3 when centered in the -52 region; W = A or T; R = A or G; N = any base).
The above promoter sequences are recognized only by RNA polymerase holoenzyme containing sigma-70. RNA polymerase holoenzymes containing other sigma factors recognize different core promoter sequences.
     upstream                                                          downstream 
 5-XXXXXXXPPPPPPXXXXXXPPPPPPXXXXGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGXXXX-3
            -35       -10       Gene to be transcribed