Nuclear Receptors Flashcards
What are nuclear receptors?
A class of proteins found within cells that are responsible for sending steroid and thyroid hormones
What is the function of nuclear receptors?
Work with other proteins to regulate the expression of specific genes, thereby controlling the development, homeostasis, and metabolism of the organism
How are nuclear receptors unique from other receptors?
Can bind directly to DNA
How are nuclear receptors activated?
A ligand (hormone) binding to a nuclear receptor results in a conformational change in the receptor, which activates it
What is a ligand?
A molecule (hormone) that affects the receptor’s behaviour
What is the ligand for the oestrogen receptor?
Oestradiol
How do receptors bind to DNA?
Sequence specific DNA binding proteins that regulate co-activator RNA polymerase recruitment to induce transcription at target gene promoters
Why are nuclear receptors classed as transcription factors?
Have ability to bind directly to DNA and regulate expression of adjacent genes
What are the 5 domains present in nuclear receptors?
- N-terminal (amino terminus)
- C-terminal (carboxyl terminus)
- DNA binding domain
- Ligand (hormone) binding domain
- Dimerisation domain
What is unique about the DNA binding domain (DBD)?
Contain ‘zinc fingers’
What are zinc fingers?
What is their function?
Loops of protein that contain a Zn2+ atom
Can bind to specific sequences of DNA called hormone response elements
What is the case with steroid hormone receptors and zinc fingers?
In steroid hormone receptors, they are coordinated with 4 Cys residues (amino acids with sulphur) which coordinate onto the zinc and bind it into place
What is function of ligand binding domain (LBD)?
- Makes receptors specific
2. Contributes (along with DBD) to the dimerisation interface of the receptor
What is function of N-terminal?
- At the amino terminus, there is a transcription regulation domain that interacts with other proteins that regulate transcription (transcription factors)
- Contains activation function 1 (AF-1), whose action is independent of the presence of ligand
Where can the LBD be found?
At the carboxyl terminus
