ubiquitin ligase complex

Definition

Target type: cellularcomponent

A protein complex that includes a ubiquitin-protein ligase and enables ubiquitin protein ligase activity. The complex also contains other proteins that may confer substrate specificity on the complex. [GOC:jh2, PMID:9529603]

Ubiquitin ligases (E3s) are multi-protein complexes responsible for targeting specific proteins for ubiquitination, a crucial post-translational modification that regulates various cellular processes. These complexes often involve multiple components, each contributing to the specificity and efficiency of ubiquitination.

The cellular component of a ubiquitin ligase complex can be broadly categorized into three major domains:

1. **Substrate Recognition Domain:** This domain binds to the target protein, recognizing specific motifs or structural features that determine its ubiquitination fate. This domain can be highly diverse and includes various protein domains like SH2, WW, and RING finger domains, each with its own specific binding preferences.

2. **Ubiquitin Ligase Domain:** This domain directly interacts with the ubiquitin-conjugating enzyme (E2), facilitating the transfer of ubiquitin from the E2 to the target protein. The most common ubiquitin ligase domains include RING, U-box, and HECT domains. These domains interact with the E2 enzyme in distinct ways, contributing to the unique catalytic properties of different E3 ligases.

3. **Scaffolding Domain:** This domain acts as a bridge between the substrate recognition domain and the ubiquitin ligase domain, ensuring proper assembly of the E3 complex and optimal substrate binding. Scaffolding domains can be relatively simple protein-protein interaction domains or complex multi-domain structures that integrate signals from various sources, allowing for intricate regulation of ubiquitination.

In addition to these core domains, E3 complexes often incorporate other accessory proteins that contribute to their functionality. These include:

* **Adaptor Proteins:** These proteins enhance the specificity of E3 complexes by interacting with specific substrates and targeting them to the ubiquitination machinery.
* **Chaperones:** Chaperone proteins assist in the proper folding and stabilization of E3 complexes, ensuring their structural integrity and catalytic activity.
* **Regulatory Proteins:** These proteins modulate the activity of E3 complexes by influencing their assembly, substrate binding, or ubiquitination activity.

The specific composition and arrangement of these domains and accessory proteins within an E3 complex determine its unique substrate specificity, catalytic efficiency, and regulatory properties. This intricate architecture allows for the precise control of ubiquitination, a process that plays a central role in a wide range of cellular functions, including cell cycle progression, DNA repair, signal transduction, and protein degradation.'
"

Proteins (6)

Compounds (102)