Biophysical Society Thematic Meeting| Lima 2019

Revisiting the Central Dogma of Molecular Biology at the Single-Molecule Level

Poster Abstracts

57-POS Board 57 HOW THE INITIATING RIBOSOME COPES WITH PPGPP TO TRANSLATE MRNAS Daria S Vinogradova 2 ; Pavel Kasatsky 2 ; Elena Maksimova 2 ; Victor Zegarra 1 ; Alena Paleskava 2 ; Andrey L Konevega 2 ; Pohl Milón 1 ; 1 Universidad Peruana de Ciencias Aplicadas, Health Sciences Faculty, Lima, Peru 2 Petersburg Nuclear Physics Institute named by B.P. Konstantinov of NRC “Kurchatov Institute”, , Gatchina, Russian Federation Stringent response uses (p)ppGpp to reshape the bacterial proteome by acting pleiotropically on RNA and protein synthesis, allowing bacteria to colonize and persist in host environments. In this work, we study a long-lasting paradox of protein synthesis during bacterial stress. Particularly, ppGpp accumulation during bacterial starvation was shown to inhibit protein synthesis; however, a number of genes are activated, and their mRNAs are translated in vivo at high (p)ppGpp concentrations. A model bridging these sets of observations was lacking. Here, we show that the translation Initiation Factor IF2 senses the cellular ppGpp to GTP ratio and regulates the progression towards protein synthesis. Our results indicate that the affinity of GTP and the inhibitory concentration of ppGpp for 30S-bound IF2 vary depending on the programmed mRNA. Highly translated mRNAs enhanced GTP affinity for 30S complexes, resulting in fast transitions to elongation of protein synthesis. Less demanded mRNAs allowed ppGpp to compete with GTP for IF2, stalling 30S complexes until exchange of the mRNA enhances the affinity for GTP. Altogether, our data propose a novel regulatory mechanism at the onset of protein synthesis that tolerates physiological concentrations of ppGpp, and that bacteria can exploit to modulate its proteome as a function of the nutritional shift happening during infection.

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