Question

The DNA-binding domain of steroid receptors is located:

• A. at the carboxy-terminal of the receptor \
• B. at the amino-terminal of the receptor \
• C. in the central part of the receptor \
• D. randomly located depending on the specific receptor

Hint:

Nuclear receptors follow a modular architecture: N-terminus triggers activation, the center binds DNA via zinc fingers, and the C-terminus captures the hormone.

Answer 1

The Correct Option is C

Step 1: Concept Steroid hormone receptors belong to the nuclear receptor superfamily of transcription factors. They share a conserved domain structure that coordinates ligand binding and gene transcription.

Step 2: Meaning These receptors contain three main domains: an N-terminal regulatory domain, a highly conserved DNA-binding domain (DBD), and a C-terminal ligand-binding domain (LBD).

Step 3: Analysis * The amino-terminal (N-terminus) contains the variable $A/B$ domain, which houses the activation function-1 ($\text{AF-1}$) site responsible for ligand-independent transcription activation. * The carboxy-terminal (C-terminus) contains the $E/F$ domain, which forms the ligand-binding domain ($\text{LBD}$) and houses the activation function-2 ($\text{AF-2}$) site. * The central region ($C$ domain) contains the highly conserved DNA-binding domain ($\text{DBD}$), which features two zinc finger motifs that recognize specific hormone response elements ($\text{HREs}$) on the target DNA.

Step 4: Conclusion Therefore, the DNA-binding domain is located in the central core part of the steroid receptor structural layout. This corresponds to option C. Final Answer: (C)