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Definition: How can AMP-activated protein kinase (AMPK) sense energy levels in cells?

AMP-activated protein kinase (AMPK) is a key regulator of cellular energy homeostasis. It acts as a sensor that monitors the energy status of cells and coordinates various metabolic pathways to maintain energy balance.

Activation of AMPK

AMPK is activated when the cellular energy levels are low, such as during conditions of nutrient deprivation or increased energy expenditure. It senses the energy status of cells by directly sensing the ratio of AMP to ATP, two important molecules involved in energy metabolism.

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AMPK Structure and Mechanism

AMPK is a heterotrimeric protein complex consisting of three subunits: α, β, and γ. The α subunit contains the catalytic domain responsible for the phosphorylation of target proteins, while the β and γ subunits function as regulatory domains.

The γ subunit of AMPK contains four cystathionine β-synthase (CBS) domains, which bind to AMP and ATP. When the cellular energy levels are low, the ratio of AMP to ATP increases, leading to the binding of AMP to the γ subunit. This causes a conformational change in the γ subunit, exposing the catalytic domain of the α subunit and allowing it to phosphorylate downstream targets.

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Downstream Effects of AMPK Activation

Once activated, AMPK phosphorylates a wide range of target proteins involved in various metabolic pathways. These phosphorylation events result in the inhibition of energy-consuming processes, such as protein synthesis and lipid synthesis, and the activation of energy-producing processes, such as glucose uptake and fatty acid oxidation.

AMPK also regulates gene expression by phosphorylating transcription factors and coactivators involved in energy metabolism. This helps to coordinate the expression of genes involved in energy production and utilization.

Conclusion

AMP-activated protein kinase (AMPK) plays a crucial role in sensing energy levels in cells. By directly sensing the ratio of AMP to ATP, AMPK can activate or inhibit various metabolic pathways to maintain energy balance. Its activation leads to the inhibition of energy-consuming processes and the activation of energy-producing processes, ultimately helping cells adapt to changes in energy availability.

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Keywords: energy, activated, protein, activation, subunit, levels, involved, processes, kinase