A) RNA polymerase\[\to {{\alpha }_{2}}\beta {{\beta }^{1}}\delta \left( E.coli \right)\]
B) RNA polymerase\[\to {{\alpha }_{2}}\beta {{\beta }^{1}}\left( E.coli \right)\]
C) RNA polymerase\[\to {{\alpha }_{2}}\beta {{\beta }^{1}}\sigma \left( E.coli \right)\]
D) RNA polymerase\[\to {{\alpha }_{2}}{{\beta }^{2}}\sigma \left( E.coli \right)\]
Correct Answer: C
Solution :
In bacterial system like E. coli, a single RNA polymerase is responsible for synthesizing all kinds of RNAs. The bacterial RNAP consists of core enzyme \[({{\beta }^{1}}\beta {{\alpha }^{1}}{{\alpha }^{2}}\omega )\] and a sigma factor. The two largest subunits \[({{\beta }^{1}}\beta )\] of the core enzyme are involved in catalysis and the remaining three subunits \[({{\alpha }^{1}}{{\alpha }^{2}}\omega )\] take part in RNAP assembly and transcriptional regulation. The sigma factor helps in recognition of start signals on DNA molecule and directs RNA polymerase in selecting the initiation site. Different components of one molecule o E.coli RNA polymerase enzyme.| Submit and gene | Mass (kilo dalton) | Location | Possible function | |
| \[{{\alpha }_{2}}\] (rpo A) | 40 each | Core Enzyme | RNAP Assembly | |
| \[\beta \](rpo B) | 155 | Core Enzyme | \[\left. \begin{align} & \\ & \\ & \\ \end{align} \right\}\] | Catalysis |
| \[{{\beta }^{1}}\] (rpo C) | 160 | Core enzyme | Catalysis | |
| \[\omega \] (rpo-) | - | Core Enzyme | RNAP Assembly | |
| \[\sigma \] (rpo D) | 32-90 | Sigma factor | Initiation |
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