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#-35 promoter

2 public questions tagged with this topic.

Transcription in Prokaryotes

Consensus sequence of the -35 element is

Promoter anatomy reveals two conserved hexamers spaced seventeen base pairs apart. Upstream hexamer centered around -35 position consensus sequence TTGACA contacted by sigma70 region 4 helix-turn-helix domain. Downstream Pribnow box at -10 consensus TATAAT recognized by region 2. Spacer length crucial for simultaneous contact of both elements due to helical phasing. TTGACA sequence unambiguously defines -35 element, distinguishing it from -10, UP element recognized by α-CTD, or GC-rich eukaryotic SP1 site GGGCGG. Promoter strength correlates with closeness to TTGACA consensus for -35 interaction optimizing closed complex formation.

Ref: Alberts Chapter 6: -35 consensus TTGACA bacterial promoters; Watson Molecular Biology Gene Promoter table -35 element sequence

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Transcription in Prokaryotes

Which subunit recognizes the -10 and -35 promoter elements?

Within bacterial holoenzyme, sequence-specific readout of promoter consensus relies predominantly on sigma factor rather than core catalytic subunits. Sigma70 region 4.2 presents helix-turn-helix motif inserting into major groove at -35 element TTGACA, while region 2.4 interacts with -10 Pribnow box TATAAT and captures flipped bases to drive melting. α subunit C-terminal domain may touch UP element AT-rich tract, but -10 and -35 recognition is sigma intrinsic. β and β' subunits shape downstream DNA channel and catalytic Mg2+ but do not determine promoter consensus identity. Exchange of sigma alters promoter preference accordingly.

Ref: Alberts Molecular Biology Cell Chapter 6: Sigma subunit recognizes -10 -35 elements; Watson Chapter 13 Sigma-DNA contacts

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