Figure 4个  Table 2
    • Feature IC3 (early initiation) EC (elongation) IC7
      Biochemical features
      Promoter bound released like IC3
      Bubble expanding on downstream side closing upstream, opening downstream like IC3
      DNA RNA hybrid 3 bp 7-8 bp 7 bp
      5'-end of RNA part of hybrid single stranded like IC3
      RNA release frequent none like IC3
      Structural features
      Structural representatives 1QLN 1MSW, 1H38 3E2E
      Promoter binding site intact destroyed like IC3
      RNA exit channel blocked formed like IC3
      Preventing upstream bubble collapse protein RNA like IC3
      Interactions between helix C and C-terminal domain present present present
      Thumb helix bound to PBD bound to hybrid like EC

      Table 1.  Biochemical and structural features of different stages in transcription

    • Residue involved in RNA binding in the EC* Nucleotide interaction partner** Role in IC7 Role in IC3
      K441 (-1, -2) RNA interaction RNA interaction
      R425 -2 RNA interaction RNA interaction
      R394 -4 RNA interaction RNA interaction
      K389 -5 RNA interaction bound to PBD
      R386 (-5, -6) RNA interaction RNA interaction
      K172 (-5, -6) distant from RNA (part of sub domain H) distant from RNA (part of sub domain H)
      R756*** ~ -9 Promoter binding Promoter binding
      R746*** ~ -9 Promoter binding Promoter binding
      *interactions of positively charged residues according to Tahirov et al. (2002); **numbering relative to the active site, not the transcription start site; ***based on 1MSW coordinates (Yin and Steitz, 2002).

      Table 2.  Protein RNA interactions in transcription complexes