Brauns, F. | Search bioRxiv

bioRxiv2020

Bulk-surface coupling reconciles Min-protein pattern formation in vitro and in vivo

Self-organisation of Min proteins is responsible for the spatial control of cell division in Escherichia coli, and has been studied both in vivo and in vitro. Intriguingly, the protein patterns observed in these settings differ qualitatively and quantitatively. This puzzling dichotomy has not been resolved to date. Using reconstituted proteins in laterally wide microchambers with a well-controlled height, we show that the Min protein dynamics on the membrane crucially depend on bulk gradients normal to the membrane. A theoretical analysis shows that in vitro patterns at low bulk height are driven by the same lateral oscillation mode as pole-to-pole oscillations in vivo. At larger bulk height, additional vertical oscillation modes set in, marking the transition to a qualitatively different in vitro regime. Our work qualitatively resolves the Min systems in vivo/in vitro conundrum and provides important insights on the mechanisms underlying protein patterns in bulk-surface coupled systems.

biophysics↗

bioRxiv2019

Design of biochemical pattern forming systems from minimal motifs

Although molecular self-organization and pattern formation are key features of life, only very few pattern-forming biochemical systems have been identified that can be reconstituted and studied in vitro under defined conditions. A systematic understanding of the underlying mechanisms is often hampered by multiple interactions, conformational flexibility and other complex features of the pattern forming proteins. Because of its compositional simplicity of only two proteins and a membrane, the MinDE system from Escherichia coli has in the past years been invaluable for deciphering the mechanisms of spatiotemporal self-organization in cells. Here we explored the potential of reducing the complexity of this system even further, by identifying key functional motifs in the effector MinE that could be used to design pattern formation from scratch. In a combined approach of experiment and quantitative modeling, we show that starting from a minimal MinE-MinD interaction motif, pattern formation can be obtained by adding either dimerization or membrane-binding motifs. Moreover, we show that the pathways underlying pattern formation are recruitment-driven cytosolic cycling of MinE and recombination of membrane-bound MinE, and that these differ in their in vivo phenomenology.

biophysics↗