Membrane curvature and the Tol-Pal complex determine polar localization of the chemoreceptor Tar inE. coli

Abstract

18Chemoreceptors are localized at the cell poles of Escherichia coli and other rod-shaped 19 bacteria. Over the years different mechanisms have been put forward to explain this polar 20 localization; from stochastic clustering, membrane curvature driven localization, interactions 21 with the Tol-Pal complex, to nucleoid exclusion. To evaluate these mechanisms, we monitored 22 the cellular localization of the aspartate chemoreceptor Tar in different deletion mutants. We 23 did not find any indication for either stochastic cluster formation or nucleoid exclusion. 24However, the presence of a functional Tol-Pal complex appeared to be essential to retain Tar 25 at cell poles. This finding also implies that the curvature of cell poles does not attract 26 chemoreceptor complexes. Interestingly, Tar still accumulated at midcell in tol and in pal 27 deletion mutants. In these mutants, the protein appears to gather at the base of division septa, 28 a region characterised by strong membrane curvature. Chemoreceptors, like Tar, form trimer-29 of-dimers that bend the cell membrane due to a rigid tripod structure with an estimated 30 curvature of approximately 37 nm. This curvature approaches the curvature of the cell 31 membrane generated during cell division, and localization of chemoreceptor tripods at curved 32 membrane areas is therefore energetically favourable as it lowers membrane tension. Indeed, 33 when we introduced mutations in Tar that abolish the rigid tripod structure, the protein was no 34 longer able to accumulate at midcell or cell poles. These findings favour a model where 35 chemoreceptor localization in E. coli is driven by strong membrane curvature and association 36 with the Tol-Pal complex. 37 38 Importance 39 Bacteria have exquisite mechanisms to sense and to adapt to the environment they live in.40 One such mechanism involves the chemotaxis signal transduction pathway, in which 41 chemoreceptors specifically bind certain attracting or repelling molecules and transduce the 42 signals to the cell. In different rod-shaped bacteria, these chemoreceptors localize specifically 43 to cell poles. Here, we examined the polar localization of the aspartate chemoreceptor Tar in 44 3 E. coli, and found that membrane curvature at cell division sites and interaction with the Tal-45 pol protein complex, localize Tar at cell division sites, the future cell poles. This study shows 46 how membrane curvature can guide localization of proteins in a cell. 47 65 future division sites. This model is referred to as the 'stochastic nucleation model' (5-7). 66Another theory postulated that MCPs preferably assemble at the curved membrane of cell 67 poles (8). Chemoreceptors form membrane spanning trimers-of-dimers that interact at their 68 cytoplasmic domain at a slight angle thereby forming a tripod-like configuration (9). 69Consequently, the trimer of dimers prefer bend membrane areas due to the reduced curvature 70 mismatch. (10, 11). This model was recently supported by mechanically bending of whole E. 71coli cells in curve...

Protein Residues and a Novel Motif Involved in the Cellular Localization of CheZ in Azorhizobium caulinodans ORS571

“…The ratio of cells that demonstrated polar localization of CheZ AC is much lower than that of CheZ EC , indicating the role of CheZ AC localization may be different between them. Similar to CheZ in E. coli , the localization of CheZ at lateral body of A. caulinodans cells showed a typical periodic distribution, and this phenomenon may be interpreted by a “stochastic nucleation model” ( Greenfield et al, 2009 ; Saaki et al, 2018 ).…”

“…Chemotaxis proteins are localized to cellular poles using multiple strategies, including the nucleoid occlusion, Tol/Pal complex, membrane curvature, and protein-protein interactions ( Laloux and Jacobs-Wagner, 2014 ). Transmembrane E. coli chemoreceptors maintain polar localization through the Tol/Pal complex, strong membrane curvature, or nucleoid exclusion ( Santos et al, 2014 ; Neeli-Venkata et al, 2016 ; Saaki et al, 2018 ) The Tol/Pal complex is a conserved component of bacterial cell envelope, which is involved in the maintenance of cell wall integrity ( Bernadac et al, 1998 ). Other chemotaxis proteins including CheA, CheW, CheY, and CheZ locate to cellular poles based on the interaction with other chemotaxis proteins ( Sourjik and Berg, 2000 ).…”

Is Longitudinal Division in Rod-Shaped Bacteria a Matter of Swapping Axis?

“…Indicating that these D-cysteines were not accessible to PG turnover enzymes. Although many proteins involved in length growth are not present in the cell poles, many specialized sensor proteins are (for instance, the serine chemoreceptor, the DcuS/DcuR two-component system, the chemoreceptor Tar, and the Osmosensing transporter ProP; Scheu et al, 2014 ; Neeli-Venkata et al, 2016 ; Romantsov et al, 2017 ; Saaki et al, 2018 ). Thus, although poles of E. coli are inert for PG recycling, they function fully in perception of their environment.…”