title: The ftsA* gain-of-function allele of Escherichia coli and its effects on the stability and dynamics of the Z ring.
abstract: Formation of the FtsZ ring (Z ring) in Escherichia coli is the first step in the assembly of the divisome, a protein machine required for cell division. Although the biochemical functions of most divisome proteins are unknown, several, including ZipA, FtsA and FtsK, have overlapping roles in ensuring that the Z ring assembles at the cytoplasmic membrane, and that it is active. As shown previously, a single amino acid change in FtsA, R286W, also called FtsA*, bypasses the requirement for either ZipA or FtsK in cell division. In this study, the properties of FtsA* were investigated further, with the eventual goal of understanding the molecular mechanism behind the bypass. Compared to wild-type FtsA, the presence of FtsA* resulted in a modest but significant decrease in the mean length of cells in the population, accelerated the reassembly of Z rings, and suppressed the cell-division block caused by excessively high levels of FtsZ. These effects were not mediated by Z-ring remodelling, because FtsA* did not alter the kinetics of FtsZ turnover within the Z ring, as measured by fluorescence recovery after photobleaching. FtsA* was also unable to permit normal cell division at below normal levels of FtsZ, or after thermoinactivation of ftsZ84(ts). However, turnover of FtsA* in the ring was somewhat faster than that of wild-type FtsA, and overexpressed FtsA* did not inhibit cell division as efficiently as wild-type FtsA. Finally, FtsA* interacted more strongly with FtsZ compared with FtsA in a yeast two-hybrid system. These results suggest that FtsA* interacts with FtsZ in a markedly different way compared with FtsA.
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Texas Medical School, 6431 Fannin Street, Houston, TX 77030, USA.
authors.forename: Brett
authors.initials: B
authors.lastname: Geissler
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Texas Medical School, 6431 Fannin Street, Houston, TX 77030, USA.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Shiomi
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Texas Medical School, 6431 Fannin Street, Houston, TX 77030, USA.
authors.forename: William
authors.initials: W
authors.lastname: Margolin
mesh_terms: D000483:Alleles; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002455:Cell Division; D004926:Escherichia coli / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D011485:Protein Binding; D020798:Two-Hybrid System Techniques
chemical_list: D018797:Cell Cycle Proteins; D029968:Escherichia coli Proteins; C489310:FtsA protein, E coli; C076835:FtsZ84 protein, E coli