In vivo structure of the E. coli FtsZ-ring revealed by photoactivated localization microscopy (PALM)

• Published in: PloS one 2010-09, Vol.5 (9), p.e12682
• Main Authors: Fu, Guo, Huang, Tao, Buss, Jackson, Coltharp, Carla, Hensel, Zach, Xiao, Jie
• Format: Article
• Language: English
• Subjects: Archives & records; Bacteria; Bacterial proteins; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biophysics; Biophysics/Experimental Biophysical Methods; Biophysics/Macromolecular Assemblies and Machines; Cell Biology/Cell Growth and Division; Cell cycle; Cell division; Cloning; Contractility; Crystal structure; Cytokinesis; Cytoplasm; Cytoskeletal Proteins - chemistry; Cytoskeletal Proteins - genetics; Cytoskeletal Proteins - metabolism; Diffraction; E coli; Electron microscopy; Escherichia coli; Escherichia coli - chemistry; Escherichia coli - genetics; Escherichia coli - metabolism; Fluorescence; Fluorescence microscopy; FtsZ protein; Gene expression; Guanosine triphosphatases; Guanosinetriphosphatase; Hypotheses; Image resolution; imaging; In vivo methods and tests; Laboratories; Light diffraction; Light microscopy; Localization; Medicine; Microscopy, Fluorescence - methods; Packing; Packing density; Palm; Protein Conformation; Protein Structure, Secondary; Proteins; scaffolds; Spatial discrimination; Spatial resolution; Structure-function relationships; Tubulin
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0012680

The FtsZ protein, a tubulin-like GTPase, plays a pivotal role in prokaryotic cell division. In vivo it localizes to the midcell and assembles into a ring-like structure-the Z-ring. The Z-ring serves as an essential scaffold to recruit all other division proteins and generates contractile force for cytokinesis, but its supramolecular structure remains unknown. Electron microscopy (EM) has been unsuccessful in detecting the Z-ring due to the dense cytoplasm of bacterial cells, and conventional fluorescence light microscopy (FLM) has only provided images with limited spatial resolution (200-300 nm) due to the diffraction of light. Hence, given the small sizes of bacteria cells, identifying the in vivo structure of the Z-ring presents a substantial challenge. Here, we used photoactivated localization microscopy (PALM), a single molecule-based super-resolution imaging technique, to characterize the in vivo structure of the Z-ring in E. coli. We achieved a spatial resolution of ∼35 nm and discovered that in addition to the expected ring-like conformation, the Z-ring of E. coli adopts a novel compressed helical conformation with variable helical length and pitch. We measured the thickness of the Z-ring to be ∼110 nm and the packing density of FtsZ molecules inside the Z-ring to be greater than what is expected for a single-layered flat ribbon configuration. Our results strongly suggest that the Z-ring is composed of a loose bundle of FtsZ protofilaments that randomly overlap with each other in both longitudinal and radial directions of the cell. Our results provide significant insight into the spatial organization of the Z-ring and open the door for further investigations of structure-function relationships and cell cycle-dependent regulation of the Z-ring.