Question

RNA polymerase subunit that recognizes and binds to promoter is
A. α-subunit
B. β-subunit
C. γ-subunit
D. σ-subunit

Answer 1

Hint: The σ subunit of RNAP is involved in all stages of transcription initiation as well as preparing of RNA synthesis, abortive initiation, promoter recognition and opening and promoter escape.

Complete Answer:
RNA polymerase is an enzyme that is involved for copying a DNA sequence into an RNA sequence, during the functioning of transcription. As complicated molecules consist of protein subunits, these RNA polymerase maintain the functioning of transcription, during that period the information kept in a molecule of DNA is duplicated into a new molecule of messenger RNA.

Now, let us find the solution from the option.
- RNA polymerases are also called as DNA directed RNA polymerases that are the reason for the polymerization of ribonucleotides into a sequence complementing the template DNA.
- RNA polymerases are enzymes which consist of a different quantity of subunits.
- α subunit begins and operates the core alignment to develop a platform on which the beta subunits can react.
- β subunit participates in chain initiation and catalysis of polynucleotide production in the template dependent manner.
- γ subunit provides alignment of RNA polymerase (RNAP) and balances assembled RNAP.
- σ subunit is a protein subunit which is required only for the beginning of RNA formation. It is a bacterial transcription starting subunit which allows particular binding of RNA polymerase to gene promoters.

Thus, the correct option is D. i.e. σ-subunit.

Note: The eubacterial RNA polymerase σ subunit allows the holoenzyme to specify and bind to particular sites on DNA called as promoters. Bacteria from a variety of regular possess more than one σ subunits that permit RNA polymerase to use different categories of promoters. It is not mentioned how sigma subunits function to change the specialty for promoter binding by RNA polymerase.