Přehled o publikaci

Compartmentalization is a hallmark of living cells that allows them to perform complex tasks by dynamically coordinating matter and energy fluxes in space and time. This compartmentalization of membrane-less organelles in prokaryotes is driven by Liquid-Liquid Phase Separation (LLPS). Studies have shown LLPS to be a major driving force in the subcellular organization of bacterial cells. These biomolecular condensates are comprised of proteins that are generally rich in intrinsically disordered regions (IDRs). In prokaryotes, translation Initiation Factor 2 (IF-2) is a GTPase that binds the initiator tRNA and catalyzes the ribosomal subunit joining to form the elongation competent 70S complex. A large portion of the N-terminal domain of IF-2 contains IDRs, making the protein a favorable candidate to form LLPS. Additionally, due to the dynamic behaviour of the N-terminus of IF-2 the structure of the full-length protein is still missing. Therefore, the mechanistic understanding of its functional role is quite elusive, especially in ribosomal subunit joining. Here, we present biochemical evidence that IF-2 can phase separate under specific conditions. The IF-2 LLPS formation can provide deeper insight into compartmentalized translation machinery in bacterial cells. We also use timeresolved cryo-EM to capture intermediate states of the initiation process using native GTP and its non-hydrolysable analogue GDPCP. Here, the main goal is to gain structural insight about the disorded N-terminus of IF-2 and its role in ribosomal subunit joining.