Describe the structure of RNA polymerase in bacteria. What is the core enzyme? What is the role of the σ subunit?

Key Concepts

RNA Polymerase Structure

RNA polymerase in bacteria is a multi-subunit enzyme responsible for synthesizing RNA from a DNA template. It consists of a core enzyme made up of multiple subunits, typically two alpha (α) subunits, one beta (β) subunit, one beta prime (β') subunit, and one omega (ω) subunit. This core enzyme is essential for the catalytic activity of RNA synthesis.

Core Enzyme

The core enzyme of bacterial RNA polymerase is the part that carries out the actual synthesis of RNA. It is capable of elongating RNA chains but cannot initiate transcription on its own. The core enzyme must associate with a σ (sigma) factor to form a holoenzyme, which is necessary for recognizing and binding to specific promoter regions on the DNA.

σ (Sigma) Subunit

The σ subunit is a crucial component of the bacterial RNA polymerase holoenzyme that facilitates the initiation of transcription. It helps the core enzyme recognize and bind to specific promoter sequences on the DNA, ensuring that transcription starts at the correct location. Once RNA synthesis begins, the σ subunit often dissociates, allowing the core enzyme to continue elongating the RNA strand.