title: Effects of pH and ionic strength on the assembly and bundling of FtsZ protofilaments: a possible role of electrostatic interactions in the bundling of protofilaments.
abstract: Assembly, bundling and stability of FtsZ protofilaments are important for the formation and functioning of the cytokinetic Z-ring during bacterial division. We found that the bundling of FtsZ protofilaments decreased strongly with increasing pH from 6.0 to 7.9, while the assembly of FtsZ monomers did not decrease considerably. In addition, the disassembly of FtsZ protofilaments was strongly suppressed at pH 6.0 as compared to the elevated pHs. The far-UV circular dichroism spectra of the native FtsZ and the tryptophan emission spectra of mutated FtsZ (Y371W) did not change by increasing pH from 6 to 7.9 indicating that the structure of FtsZ was not altered significantly. Further, the inhibition of bundling of FtsZ protofilaments predominantly, and the inhibition of assembly to a lesser extent by salt indicated that electrostatic interactions are important for the assembly and bundling of FtsZ protofilaments. These observations are supported by the results of computational docking of Escherichia coli dimer structure. The results suggest that the basic intracellular pH (7.4-7.8) of E. coli may play a role in regulating the assembly dynamics of FtsZ in the Z-ring by reducing protofilament stability and bundling in bacterial cytoplasm.
authors.affiliation: School of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
authors.forename: Tushar K
authors.initials: TK
authors.lastname: Beuria
authors.forename: Jaimin H
authors.initials: JH
authors.lastname: Shah
authors.forename: Manas K
authors.initials: MK
authors.lastname: Santra
authors.forename: Vinay
authors.initials: V
authors.lastname: Kumar
authors.forename: Dulal
authors.initials: D
authors.lastname: Panda
mesh_terms: D004926:Escherichia coli / Q000737:chemistry; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D020558:GTP Phosphohydrolases / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008854:Microscopy, Electron; D008958:Models, Molecular; D046912:Multiprotein Complexes; D009994:Osmolar Concentration; D020836:Protein Structure, Quaternary; D055672:Static Electricity
chemical_list: D029968:Escherichia coli Proteins; C076835:FtsZ84 protein, E coli; D046912:Multiprotein Complexes; D020558:GTP Phosphohydrolases