Phase separation of TmaR - a novel polar protein that controls cell metabolism by spatial sequestration of a major sugar regulator

The scarcity of membrane-bounded organelles led in the past to the assumption that macromolecules are not specifically localized in bacteria. This view has changed considerably in recent years, and we now know that many proteins and RNAs are specifically localized in bacteria.

The poles of rod-shape bacteria emerge as hubs for a unique population of macromolecules, suggesting that bacterial cells have distinct subcellular domains that can be referred to as membrane-less organelles.

In a recent study, we discovered a conserved polar protein of an unknown function that controls the activity of EI, a major regulator of sugar metabolism, by keeping it inactive at the poles of E. coli cells. Hence, we termed this protein TmaR for targeting of a metabolism-associated regulator.

TmaR is predicted to form a coiled coil and to contain intrinsically disordered regions (IDR). It also has a high content of charged residues, and is predicted to be a nucleic acid-binding protein.

I will present evidence that TmaR phase separates both in vivo and in vitro.

Studies of TmaR are expected to shed light on the mechanism that underlies its localization and function and on regulation of bacterial cell organization by phase separation in general.