Septal localization of FtsQ, an essential cell division protein in Escherichia coli - PubMed (original) (raw)

Septal localization of FtsQ, an essential cell division protein in Escherichia coli

J C Chen et al. J Bacteriol. 1999 Jan.

Abstract

Septation in Escherichia coli requires several gene products. One of these, FtsQ, is a simple bitopic membrane protein with a short cytoplasmic N terminus, a membrane-spanning segment, and a periplasmic domain. We have constructed a merodiploid strain that expresses both FtsQ and the fusion protein green fluorescent protein (GFP)-FtsQ from single-copy chromosomal genes. The gfp-ftsQ gene complements a null mutation in ftsQ. Fluorescence microscopy revealed that GFP-FtsQ localizes to the division site. Replacing the cytoplasmic and transmembrane domains of FtsQ with alternative membrane anchors did not prevent the localization of the GFP fusion protein, while replacing the periplasmic domain did, suggesting that the periplasmic domain is necessary and sufficient for septal targeting. GFP-FtsQ localization to the septum depended on the cell division proteins FtsZ and FtsA, which are cytoplasmic, but not on FtsL and FtsI, which are bitopic membrane proteins with comparatively large periplasmic domains. In addition, the septal localization of ZipA apparently did not require functional FtsQ. Our results indicate that FtsQ is an intermediate recruit to the division site.

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Figures

FIG. 1

FIG. 1

Subcellular locations of GFP-FtsQ (A), GFP-FFQ (B), and GFP (C). Cells were grown and prepared for microscopy as described in Materials and Methods. Strains used were EC442 (A), JOE196 (B), and EC452 (C). Bar, 10 μm.

FIG. 2

FIG. 2

Immunoblot of FtsQ and GFP-FtsQ fusion proteins. Lanes: 1, MC4100; 2 to 6, serial dilutions of EC442; 7, MC4100; 8, JOE192; 9, JOE193; 10, JOE196; 11, JOE194. Cells were grown at 30°C to the early log phase and boiled in SDS sample buffer as described in Materials and Methods. Equivalent amounts of samples were loaded except that for lanes 3 to 6, the sample in lane 2 was diluted 1/5, 1/10, 1/15, and 1/20, respectively, with SDS sample buffer. The positions of GFP-FtsQ and FtsQ are indicated on the right.

FIG. 3

FIG. 3

Localization of GFP-FtsQ in fts mutants. (A and B) GFP-FtsQ localizes to division sites in ftsZ84(Ts) (A) and ftsA12(Ts) (B) cells at 30°C (left panels) but not at 42°C (middle panels); DAPI images indicate that nucleoid structures are normal in the filaments at 42°C (right panels). (C and D) GFP-FtsQ localizes to potential division sites in FtsI (C) and FtsL (D) depletion strains; the left panels are GFP images of cells growing normally in the presence of arabinose, the middle panels are GFP images of cells grown with glucose and therefore depleted of FtsI or FtsL, and the right panels are corresponding DAPI images of the middle panels. Cells were grown and fixed for fluorescence microscopy as described in Materials and Methods. Strains used were JOE97 (A), JOE95 (B), JOE233 (C), and JOE220 (D). Bar, 10 μm.

FIG. 4

FIG. 4

Localization of ZipA-GFP in an ftsQ1(Ts) mutant. (Left) GFP image of JOE165 cells grown at 30°C. (Right) GFP image of JOE165 cells grown at 42°C for 45 min. Cells were fixed for microscopy as described in Materials and Methods. Bar, 10 μm.

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