title: Charged Molecules Modulate the Volume Exclusion Effects Exerted by Crowders on FtsZ Polymerization.
abstract: We have studied the influence of protein crowders, either combined or individually, on the GTP-induced FtsZ cooperative assembly, crucial for the formation of the dynamic septal ring and, hence, for bacterial division. It was earlier demonstrated that high concentrations of inert polymers like Ficoll 70, used to mimic the crowded cellular interior, favor the assembly of FtsZ into bundles with slow depolymerization. We have found, by fluorescence anisotropy together with light scattering measurements, that the presence of protein crowders increases the tendency of FtsZ to polymerize at micromolar magnesium concentration, being the effect larger with ovomucoid, a negatively charged protein. Neutral polymers and a positively charged protein also diminished the critical concentration of assembly, the extent of the effect being compatible with that expected according to pure volume exclusion models. FtsZ polymerization was also observed to be strongly promoted by a negatively charged polymer, DNA, and by some unrelated polymers like PEGs at concentrations below the crowding regime. The influence of mixed crowders mimicking the heterogeneity of the intracellular environment on the tendency of FtsZ to assemble was also studied and nonadditive effects were found to prevail. Far from exactly reproducing the bacterial cytoplasm environment, this approach serves as a simplified model illustrating how its intrinsically crowded and heterogeneous nature may modulate FtsZ assembly into a functional Z-ring.
authors: Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain.
authors: Begoña
authors: B
authors: Monterroso
authors: Instituto de Química-Física Rocasolano, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain.
authors: Belén
authors: B
authors: Reija
authors: Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain.
authors: Mercedes
authors: M
authors: Jiménez
authors: Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain.|Instituto de Química-Física Rocasolano, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain.
authors: Silvia
authors: S
authors: Zorrilla
authors: Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain.
authors: Germán
authors: G
authors: Rivas
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000648:ultrastructure; D003598:Cytoskeletal Proteins / Q000737:chemistry* / Q000648:ultrastructure; D004926:Escherichia coli; D029968:Escherichia coli Proteins / Q000737:chemistry*; D005362:Ficoll / Q000737:chemistry; D007477:Ions; D010059:Ovomucin / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D012259:Ribonuclease, Pancreatic / Q000737:chemistry; D012996:Solutions
chemical_list: D001426:Bacterial Proteins; D003598:Cytoskeletal Proteins; D029968:Escherichia coli Proteins; C071525:FtsZ protein, Bacteria; D007477:Ions; D012996:Solutions; D005362:Ficoll; D010059:Ovomucin; D011092:Polyethylene Glycols; D012259:Ribonuclease, Pancreatic