Cul4B-RING E3 ubiquitin ligase complex

Definition

Target type: cellularcomponent

A ubiquitin ligase complex in which a cullin from the Cul4B subfamily and a RING domain protein form the catalytic core; substrate specificity is conferred by unknown subunits. [PMID:15571813, PMID:15688063]

The Cul4B-RING E3 ubiquitin ligase complex is a multi-protein assembly that plays a crucial role in protein ubiquitination, a process critical for diverse cellular functions. The complex consists of several key components, each contributing to its overall function.

1. **Cullin 4B (Cul4B):** This protein serves as the scaffold for the complex. Its N-terminal domain interacts with the RING domain of RBX1, while its C-terminal domain binds to the adaptor protein DDB1.

2. **DDB1:** This adaptor protein acts as a bridge, connecting Cul4B to substrate recognition modules called WD40 repeat proteins. These modules are specific for different target proteins, thus allowing Cul4B to regulate a wide range of cellular processes.

3. **RBX1 (RING-box protein 1):** This protein possesses a RING domain, which is essential for the complex's E3 ligase activity. The RING domain interacts with an E2 ubiquitin-conjugating enzyme, facilitating the transfer of ubiquitin from the E2 to the target protein.

4. **WD40 repeat proteins:** These proteins provide specificity to the complex by binding to specific target proteins. The WD40 repeats form a beta-propeller structure, allowing for the interaction with diverse substrates. Some examples of WD40 repeat proteins associated with Cul4B include:

* **DDB2:** This protein acts as a DNA damage sensor and is involved in nucleotide excision repair.
* **VPRBP:** This protein participates in viral restriction and is linked to immune responses.
* **CDT2:** This protein is crucial for DNA replication and cell cycle control.

5. **E2 ubiquitin-conjugating enzyme:** This enzyme plays a critical role in transferring ubiquitin from itself to the target protein. The E2 enzyme interacts with the RING domain of RBX1, facilitating this transfer step.

The Cul4B-RING E3 ubiquitin ligase complex assembles into a functional unit through intricate protein-protein interactions. The complex uses its E3 ligase activity to attach ubiquitin chains to target proteins, ultimately leading to their degradation or functional modification. This process is essential for regulating a wide range of cellular processes, including DNA damage repair, cell cycle control, immune responses, and viral restriction.'
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Proteins (2)

Compounds (10)