protein phosphatase type 1 complex

Definition

Target type: cellularcomponent

A protein complex that possesses magnesium-dependent protein serine/threonine phosphatase (AMD phosphatase) activity, and consists of a catalytic subunit and one or more regulatory subunits that dictates the phosphatase's substrate specificity, function, and activity. [GOC:mah, GOC:ssd]

The protein phosphatase type 1 (PP1) complex is a highly versatile enzyme complex that plays a critical role in regulating a wide range of cellular processes, including glycogen metabolism, muscle contraction, cell cycle progression, and signal transduction. The cellular component of the PP1 complex is a dynamic and multifaceted structure, characterized by its intricate interactions with various scaffolding proteins, regulatory subunits, and target enzymes.

At its core, the PP1 complex consists of the catalytic subunit, PP1, which possesses the enzymatic activity responsible for dephosphorylating target proteins. This catalytic subunit associates with a diverse array of regulatory subunits, including the targeting subunits that direct the PP1 complex to specific cellular locations and substrates. These regulatory subunits can be classified into distinct families, including:

1. **Targeting Subunits:** These subunits play a crucial role in determining the subcellular localization and substrate specificity of the PP1 complex. They often bind to specific cellular structures, such as the cytoskeleton, glycogen granules, or nuclear components, and recruit PP1 to these sites. Examples of targeting subunits include:
- **Myosin-binding subunit (MBS):** Associates with myosin filaments and regulates muscle contraction.
- **Glycogen-targeting subunit (Gu003csubu003eMu003c/subu003e):** Localizes PP1 to glycogen granules and controls glycogen metabolism.
- **Nuclear targeting subunit (NIPP1):** Directs PP1 to the nucleus and regulates gene expression.

2. **Inhibitory Subunits:** These subunits modulate the activity of PP1 by inhibiting its catalytic activity. They can act as "brakes" on PP1, preventing it from dephosphorylating its substrates until specific signals are received. Examples of inhibitory subunits include:
- **Inhibitor-1 (I-1):** Inhibits PP1 activity in response to stress signals.
- **Inhibitor-2 (I-2):** Regulates PP1 activity in the context of glycogen metabolism.

3. **Activatory Subunits:** These subunits can enhance the activity of PP1 by increasing its affinity for certain substrates or by protecting it from inhibition. Examples of activatory subunits include:
- **Reversible phosphorylation:** Phosphorylation of PP1 can modulate its activity, either enhancing or inhibiting its function depending on the specific phosphorylation site.
- **Small molecule inhibitors:** Certain small molecules can bind to PP1 and modulate its activity.

The cellular component of the PP1 complex is not a static structure but rather a dynamic entity that constantly adapts to changing cellular conditions. The association and dissociation of regulatory subunits, as well as the phosphorylation state of PP1, play crucial roles in fine-tuning the activity and localization of the complex. Through these intricate interactions, the PP1 complex ensures the precise regulation of a wide range of cellular processes, contributing to cellular homeostasis and proper function.'
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Proteins (1)

Compounds (1)