Question

Which one of the following lacks active site of RNA polymerase?

• A. $\alpha {\alpha }^{\prime }\beta 2\sigma$
• B. $\alpha \beta {\beta }^{\prime }\sigma$
• C. $\alpha {\alpha }^{\prime }\beta ,{\beta }^{\prime }\sigma$
• D. ${\alpha }_2\beta {\beta }^{\prime }$

Answer 1

Answer: (D)

${\alpha }_2\beta {\beta }^{\prime }$

The DNA-dependent RNA polymerase of is a large, complex, holoenzyme. It has five core subunits (Mr 390,000) and a sixth subunit. The five core units are two copies of alpha subunit, one copy of each beta, beta prime and omega subunit. The sigma subunit carries active site of the enzyme and binds transiently to the core to direct the enzyme to specific binding sites on the DNA. Thus the core enzyme (${\alpha }_2\beta {\beta }^{\prime }$) lacks active site. Correct answer is D.