When Too Much ATP Is Bad for Protein Synthesis

• Cell's energy and protein synthesis potentials depend on the availability of Mg2 +.
• Bacteria sense and respond to various degrees of Mg2 + limitation.
• Non-physiological increase in ATP disrupts essential Mg2 +-dependent processes.
• Cell restores free Mg2 + levels by shutting down synthesis of ATP and ribosomes.

Adenosine triphosphate (ATP) is the energy currency of living cells. Even though ATP powers virtually all energy-dependent activities, most cellular ATP is utilized in protein synthesis via tRNA aminoacylation and guanosine triphosphate regeneration. Magnesium (Mg2 +), the most common divalent cation in living cells, plays crucial roles in protein synthesis by maintaining the structure of ribosomes, participating in the biochemistry of translation initiation and functioning as a counterion for ATP. A non-physiological increase in ATP levels hinders growth in cells experiencing Mg2 + limitation because ATP is the most abundant nucleotide triphosphate in the cell, and Mg2 + is also required for the stabilization of the cytoplasmic membrane and as a cofactor for essential enzymes. We propose that organisms cope with Mg2 + limitation by decreasing ATP levels and ribosome production, thereby reallocating Mg2 + to indispensable cellular processes.

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