Question:
The products of which of the following pair of nif genes control the expression of other nif genes?
The products of which of the following pair of nif genes control the expression of other nif genes?
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Remember: NifA is the Activator, and NifL is the Limiter/inhibitor of nitrogen fixation gene transcription.
Updated On: Jul 13, 2026
- nif D and nif K
- nif A and nif L
- nif N and nif Q
- nif H and nif E
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The Correct Option is B
Solution and Explanation
Step 1: Understanding the Concept:
Biological nitrogen fixation is carried out by prokaryotes using nitrogenase enzymes encoded by the complex multi-operon nif gene cluster. Expression of these genes is tightly regulated by specific environmental sensors and transcriptional factors.
Step 2: Detailed Explanation:
- The expression of the nif genes is regulated by the regulatory proteins encoded by {nifA and {nifL:
- NifA acts as a transcriptional activator that binds to the promoter regions of other nif operons, initiating their transcription.
- NifL acts as a sensor of oxygen and fixed nitrogen levels. When oxygen levels are high or fixed nitrogen is abundant, NifL binds to NifA and inhibits its activity, preventing the synthesis of nitrogenase.
- nifDK encodes the catalytic $\alpha$ and $\beta$ subunits of nitrogenase component I.
- nifH encodes the Fe-protein component II.
Step 3: Final Answer:
The regulatory pair controlling other nif genes is nifA and nifL.
Biological nitrogen fixation is carried out by prokaryotes using nitrogenase enzymes encoded by the complex multi-operon nif gene cluster. Expression of these genes is tightly regulated by specific environmental sensors and transcriptional factors.
Step 2: Detailed Explanation:
- The expression of the nif genes is regulated by the regulatory proteins encoded by {nifA and {nifL:
- NifA acts as a transcriptional activator that binds to the promoter regions of other nif operons, initiating their transcription.
- NifL acts as a sensor of oxygen and fixed nitrogen levels. When oxygen levels are high or fixed nitrogen is abundant, NifL binds to NifA and inhibits its activity, preventing the synthesis of nitrogenase.
- nifDK encodes the catalytic $\alpha$ and $\beta$ subunits of nitrogenase component I.
- nifH encodes the Fe-protein component II.
Step 3: Final Answer:
The regulatory pair controlling other nif genes is nifA and nifL.
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