PMID:20516200

Citation	Fleming, TC, Shin, JY, Lee, SH, Becker, E, Huang, KC, Bustamante, C and Pogliano, K (2010) Dynamic SpoIIIE assembly mediates septal membrane fission during Bacillus subtilis sporulation. Genes Dev. 24:1160-72
Abstract	SpoIIIE is an FtsK-related protein that transports the forespore chromosome across the Bacillus subtilis sporulation septum. We use membrane photobleaching and protoplast assays to demonstrate that SpoIIIE is required for septal membrane fission in the presence of trapped DNA, and that DNA is transported across separate daughter cell membranes, suggesting that SpoIIIE forms a channel that partitions the daughter cell membranes. Our results reveal a close correlation between septal membrane fission and the assembly of a stable SpoIIIE translocation complex at the septal midpoint. Time-lapse epifluorescence, total internal reflection fluorescence (TIRF) microscopy, and live-cell photoactivation localization microscopy (PALM) demonstrate that the SpoIIIE transmembrane domain mediates dynamic localization to active division sites, whereas the assembly of a stable focus also requires the cytoplasmic domain. The transmembrane domain fails to completely separate the membrane, and it assembles unstable foci. TIRF microscopy and biophysical modeling of fluorescence recovery after photobleaching (FRAP) data suggest that this unstable protein transitions between disassembled and assembled oligomeric states. We propose a new model for the role of SpoIIIE assembly in septal membrane fission that has strong implications for how the chromosome terminus crosses the septum.
Links	PubMed PMC2878653 Online version:10.1101/gad.1925210
Keywords	Bacillus subtilis/genetics; Bacillus subtilis/growth & development; Bacillus subtilis/metabolism; Bacillus subtilis/physiology; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Cell Membrane/metabolism; DNA, Fungal/metabolism; Fluorescence Recovery After Photobleaching; Models, Biological; Mutation; Protein Folding; Protein Structure, Tertiary; Protein Transport; Spores, Bacterial/growth & development
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
BACSU:SP3E		GO:0043936: asexual sporulation resulting in formation of a cellular spore	ECO:0000315:		P		Figure 1. SpoIIIE is required for septal membrane fission. (B,C) Protoplast assays for septal membrane fission in wild type (B) and ΔspoIIIE (C), showing cell membranes (red) and DNA (green).	complete

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