## 1 Early Research on the Structure of Bacterial RNA Polymerase
\begin{table}
\begin{tabular}{l l l l} \hline \hline
**Structure** & **PDB code** & **Reference** & **Source** \\ \hline Subunit and domain & & & \\ \hline \(\alpha\) subunit NTD & 1 BDF\({}^{\mathrm{X}}\) & [7] & A \\ \(\alpha\) subunit NTD & 4 NOI\({}^{\mathrm{X}}\) & none & F \\ \(\alpha\) subunit CTD & 1 COO\({}^{\mathrm{N}}\), 3K4G\({}^{\mathrm{X}}\) & [5,8] & A \\ \(\alpha\) subunit CTD & 1 DOQ\({}^{\mathrm{N}}\) & [9] & B \\ \(\alpha\) subunit CTD & 2 MAX\({}^{\mathrm{N}}\) & [10] & E \\ \hline \(\beta\) subunit 2/i4 domains & 3 LTI\({}^{\mathrm{X}}\) & [11] & A \\ \(\beta\) subunit flap domain & 2 LY7\({}^{\mathrm{N}}\) & none & C \\ \(\beta\) subunit 1/2 domains & 4 KBJ\({}^{\mathrm{X}}\) & [12] & I \\ \hline \(\beta\) subunit i2 domain & 2 AUJ\({}^{\mathrm{X}}\) & [13] & B \\ \(\beta\) subunit i6 domain & 2 AUK\({}^{\mathrm{X}}\), 4 IQZ\({}^{\mathrm{X}}\) & [13] & A \\ \hline \(\sigma\) region 1.1 & 2K6X\({}^{\mathrm{N}}\) & [14] & G, a \\ \(\sigma^{\mathrm{70}}\) domain2 & 1 SIG\({}^{\mathrm{X}}\) & [15] & A, a \\ \(\sigma^{\mathrm{A}}\) domains2 and 3 & 1 KU2\({}^{\mathrm{X}}\) & [16] & B, a \\ \(\sigma^{\mathrm{A}}\) domain4 & 1 KU3\({}^{\mathrm{X}}\) & [16] & B, a \\ \(\sigma^{\mathrm{A}}\) domain4–DNA (–35 element) & 1 KU7\({}^{\mathrm{X}}\) & [16] & B, a \\ \(\sigma^{\mathrm{A}}\) domain4 & 1 TTY\({}^{\mathrm{N}}\) & [17] & G, a \\ \(\sigma^{\mathrm{A}}\) domain2–DNA (–10 element) & 3 UGO\({}^{\mathrm{X}}\), 3 UGP\({}^{\mathrm{X}}\) & [18] & B, a \\ \(\sigma^{\mathrm{A}}\) domain4–\(\alpha\)CTD–DNA & 3N97\({}^{\mathrm{X}}\) & none & B, a, A \\ \hline \(\sigma^{\mathrm{N}}\)RpoN–DNA (–24 element) & 2O8K\({}^{\mathrm{N}}\), 2O9I\({}^{\mathrm{N}}\) & [19] & D, d \\ \(\sigma^{\mathrm{N}}\) core binding domain & 2K9M\({}^{\mathrm{N}}\) & [20] & D, d \\ \(\sigma^{\mathrm{N}}\)RpoN domain & 2 AHQ\({}^{\mathrm{N}}\) & [21] & D, d \\ \hline \(\sigma^{\mathrm{E}}\)domain4–DNA (–35 element) & 2H27\({}^{\mathrm{X}}\) & [22] & A, c \\ \(\sigma^{\mathrm{C}}\) domain2 & 2O7G\({}^{\mathrm{X}}\) & [23] & I, c \\ \(\sigma^{\mathrm{C}}\) domain4 & 2O8X\({}^{\mathrm{X}}\) & [23] & I, c \\ \(\sigma^{\mathrm{D}}\) domain4 & 3 VFZ\({}^{\mathrm{X}}\) & [24] & I, c \\ \hline \(\delta\) subunit NTD & 2 KRC\({}^{\mathrm{N}}\), 4 NC7\({}^{\mathrm{X}}\), 4 NC8\({}^{\mathrm{X}}\), & [25, 26, 27] & C \\  & 2M4K\({}^{\mathrm{N}}\), 2 KRC\({}^{\mathrm{N}}\) & & \\ \(\varepsilon\) subunit & 4 NJC\({}^{\mathrm{X}}\) & [28] & C \\ \hline RNAP & & & \\ \hline Core enzyme & 1 HQM\({}^{\mathrm{X}}\) & [29,30] & B \\ Core enzyme (\(\Delta\)\(\alpha\) subunit) & 2 GHO\({}^{\mathrm{X}}\) & [31] & B \\ Holoenzyme & 1L9U\({}^{\mathrm{X}}\), 1 IW7\({}^{\mathrm{X}}\), 2A6E\({}^{\mathrm{X}}\), & [32, 33, 34] & B \\  & 2 CW0\({}^{\mathrm{X}}\) & & \\ Holoenzyme & 4 YG2\({}^{\mathrm{X}}\), 4 LJZ\({}^{\mathrm{X}}\), 4 MEY\({}^{\mathrm{X}}\) & [35, 36, 37] & A \\ Holoenzyme–DNA (–41 \(\sim\) –7) & 1L9Z\({}^{\mathrm{X}}\) & [38] & B \\ Holoenzyme–DNA (–12 \(\sim\) +12) & 4G7H\({}^{\mathrm{X}}\), 4G7O\({}^{\mathrm{X}}\) & [39] & B \\ _de novo_ initiation complex & 4Q4Z\({}^{\mathrm{X}}\), 4 OIO\({}^{\mathrm{X}}\) & [40,41] & B \\ Initially transcribing complex & 4Q5S\({}^{\mathrm{X}}\) & [40] & B \\ Elongation complex & 2O5I\({}^{\mathrm{X}}\), 2O5J\({}^{\mathrm{X}}\) & [42,43] & B \\ Paused elongation complex & 4 GZY\({}^{\mathrm{X}}\), 4 GZZ\({}^{\mathrm{X}}\) & [44] & B \\ Backtracked elongation complex & 4 WQS\({}^{\mathrm{X}}\) & [45] & B \\ \hline \hline \multicolumn{4}{l}{A: _Escherichia coli_; B: _Thermus aquatics/Thermus thermophilus_; C: _Bacillus subtilis/Bacillus stearothermophilus_; D: _Aquifex aeolicus_; E: _Helicobacter pylori_; F: _Campylobacter jejuni_; G: _Thermotoga maritime_; I: _Mycobacterium tuberculosis_; a: group I \(\circ\) factor; c: extracrotoplasmic function (ECF) \(\sigma\) factor; d: \(\sigma^{\mathrm{N}}\)/\(\sigma^{\mathrm{54}}\) factor; \({}^{\mathrm{X}}\): X-ray crystallography method; \({}^{\mathrm{N}}\): NMR method.} \\ \end{tabular}
\end{table} 
Table 1: Structural information on bacterial RNAP.