Interplay of Mg2+, ADP, and ATP in the cytosol and mitochondria: unravelling the role of Mg2+ in cell respiration.
Level 5 - mechanism / opinion, no new human data
Bench and in vitro/in vivo plant cell research without human data.
PubMed 25313036 · doi:10.1073/pnas.1406251111
What was done
Researchers developed in vivo and in vitro 31P-NMR spectroscopy techniques to simultaneously quantify free and complexed Mg2+, ADP, and ATP in subcellular compartments (cytosol and mitochondria) of heterotrophic sycamore (Acer pseudoplatanus L.) cells under varying nutrient conditions and Mg2+ starvation.
What was found
Cytosolic concentrations of ADP and Mg2+ were low and stable, whereas mitochondrial matrix [Mg2+] was tenfold higher. ADP was mainly free in the cytosol but complexed by Mg2+ in the mitochondrial matrix, while ATP was mostly complexed with Mg2+ in both compartments. Mg2+ starvation reversibly increased free nucleotide concentrations in both compartments, increased ADP at the expense of ATP, decreased coupled respiration, and arrested cell growth. The abstract did not report absolute numerical concentrations or variance.
Why it matters
This work demonstrates that plant cell respiration is primarily regulated by cytosolic ADP concentration rather than the ATP/ADP ratio or energy charge, modulated by compartmentalized Mg2+ gradients.
Limits
Measurements were restricted to cultured plant cells (sycamore), so findings may not directly translate to animal or human physiology. Replicate counts and exact numerical baseline concentrations were not reported in the abstract.
Cited by
- context 65 percent of intracellular magnesium is bound to ATP in mitochondria.