Abstract
Intracellular protein gradients are significant determinants of spatial organization. However, little is known about how protein patterns are established, and how their positional information directs downstream processes. We have accomplished the reconstitution of a protein concentration gradient that directs the assembly of the cell division machinery in E.coli from the bottom-up. Reconstituting self-organized oscillations of MinCDE proteins in membrane-clad soft-polymer compartments, we demonstrate that distinct time-averaged protein concentration gradients are established. Our minimal system allows to study complex organizational principles, such as spatial control of division site placement by intracellular protein gradients, under simplified conditions. In particular, we demonstrate that FtsZ, which marks the cell division site in many bacteria, can be targeted to the middle of a cell-like compartment. Moreover, we show that compartment geometry plays a major role in Min gradient establishment, and provide evidence for a geometry-mediated mechanism to partition Min proteins during bacterial development.
Highlights
Intracellular concentration gradients of proteins in micrometer-sized cells have long been thought to be unsustainable due to diffusion
Previous controls with purified Min proteins on flat bilayers and the non-hydrolysable ATP analog ATPγS confirmed that the dynamic protein patterns were thereby powered by ATP (Loose et al, 2008)
The membrane potential (Strahl and Hamoen, 2010) and molecular crowding in a living cell could influence Min protein patterns
Summary
Intracellular concentration gradients of proteins in micrometer-sized cells have long been thought to be unsustainable due to diffusion. The past decade revealed the existence of multiple intracellular gradients in eukaryotes and prokaryotes and their significance in providing positional information within the cellular compartment (Kiekebusch and Thanbichler, 2014). These protein gradients are emerging as significant general motifs to spatially organize cells, little is known about how protein patterns are established by local unmixing, and maintained on a molecular level. If more complex geometries need to be realized, or if the compartments need to be mechanically stabilized, biochemical systems may be reconstituted on and in spatially tailored microfabricated environments (Garner et al, 2007; Laan et al, 2012). Combinations of two- and three-dimensionally engineered substrates with lipid membranes
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