Question

Which promoter is commonly used for high-level expression in E. coli?

• A. Lac promoter
• B. T7 promoter
• C. SV40 promoter
• D. CMV promoter

Hint:

Expression promoters: \[ \boxed{ \begin{aligned} \text{T7 promoter} &\rightarrow \textit{E. coli} \text{CMV promoter} &\rightarrow \text{Mammalian cells} \text{SV40 promoter} &\rightarrow \text{Mammalian expression} \end{aligned} } \]

Answer 1

The Correct Option is B

Step 1: Recall promoters used in expression systems. The T7 promoter is specifically recognized by T7 RNA polymerase and drives very high levels of transcription in engineered E. coli strains.

Step 2: Eliminate other options.
• Lac promoter gives moderate expression.
• SV40 and CMV promoters are used mainly in mammalian cells. Thus, \[ \boxed{\text{T7 promoter}} \] is commonly used for high-level protein expression in E. coli. Therefore, \[ \boxed{(B)} \] is the correct answer.