Question

All nuclear receptors ...

A. Are cytosolic proteins that enter the nucleus upon ligand binding.
B. Have ligand-binding and DNA-binding domains, and can directly bind to DNA.
C. Bind to steroid hormones.
D. Are transcriptional repressors in the absence of their ligand

Answer 1

B. Have ligand-binding and DNA-binding domains, and can directly bind to DNA.

Nuclear receptors typically have ligand-binding and DNA-binding domains. They may be located in the cytoplasm or nucleus, bind to various ligands including hormones, and regulate gene transcription by directly interacting with DNA.

Step-by-step explanation:

The question is about the characteristics of nuclear receptors. Nuclear receptors are a class of proteins within cells that are responsible for sensing steroid and thyroid hormones and certain other lipids. They have a common mechanism of action that involves directly regulating the expression of target genes.

All nuclear receptors are not the same, but they typically share some key features.

Importantly, they:

• Have ligand-binding and DNA-binding domains, and can directly bind to DNA.
• Can be located in the cytoplasm or in the nucleus before ligand binding.
• Often change conformation upon ligand binding and can enter the nucleus from the cytoplasm if they are not already there.
• Bind to steroid and thyroid hormones among other ligands.
• Function as transcription regulators, acting as repressors or activators depending on the presence of ligand.

Therefore, the most accurate statement regarding nuclear receptors is that they have ligand-binding and DNA-binding domains, and can directly bind to DNA (option B).