Lipid spirals in Bacillus subtilis and their role in cell division

145

153

Cardiolipin is an ever-present component of the energy-conserving inner membranes of bacteria and mitochondria. Its modulation of the structure and dynamism of the bilayer impacts on the activity of their resident proteins, as a number of studies have shown. Here we analyze the consequences cardiolipin has on the conformation, activity, and localization of the protein translocation machinery. Cardiolipin tightly associates with the SecYEG protein channel complex, whereupon it stabilizes the dimer, creates a high-affinity binding surface for the SecA ATPase, and stimulates ATP hydrolysis. In addition to the effects on the structure and function, the subcellular distribution of the complex is modified by the cardiolipin content of the membrane. Together, the results provide rare and comprehensive insights into the action of a phospholipid on an essential transport complex, which appears to be relevant to a broad range of energy-dependent reactions occurring at membranes.

Section: Discussionmentioning

confidence: 87%

Section: Localization Of Secyeg Is Affected By the Cardiolipin Contenmentioning

confidence: 99%

The action of cardiolipin on the bacterial translocon

Gold

Robson

Bao

et al. 2010

145

153

“…(i) Amphiphilic proteins have a high interaction potential with lipids (37). (ii) The amphiphilic, positively charged helix of MinD has a preference for association with negatively charged phospholipids (36,(38)(39)(40). (iii) CL increases the binding efficiency of MinD to liposomes in vitro (41).…”

Section: Resultsmentioning

confidence: 99%

“…The diversity of its four acyl chains may influence CL packing in microdomains and its interaction with proteins (49). Barák et al (38) described MinD as an amphiphilic protein with a membrane-associated peptide helix and a region of positive charge in contact with the membrane. The amphiphilic and cationic regions of the C terminus of MinD were reported to create hydrophobic and electrostatic interactions that interacted with anionic lipids (36).…”

Section: Discussionmentioning

confidence: 99%

Cardiolipin microdomains localize to negatively curved regions of Escherichia coli membranes

Renner¹,

Weibel

2011

307

336

Many proteins reside at the cell poles in rod-shaped bacteria. Several hypotheses have drawn a connection between protein localization and the large cell-wall curvature at the poles. One hypothesis has centered on the formation of microdomains of the lipid cardiolipin (CL), its localization to regions of high membrane curvature, and its interaction with membrane-associated proteins. A lack of experimental techniques has left this hypothesis unanswered. This paper describes a microtechnology-based technique for manipulating bacterial membrane curvature and quantitatively measuring its effect on the localization of CL and proteins in cells. We confined Escherichia coli spheroplasts in microchambers with defined shapes that were embossed into a layer of polymer and observed that the shape of the membrane deformed predictably to accommodate the walls of the microchambers. Combining this technique with epifluorescence microscopy and quantitative image analyses, we characterized the localization of CL microdomains in response to E. coli membrane curvature. CL microdomains localized to regions of high intrinsic negative curvature imposed by microchambers. We expressed a chimera of yellow fluorescent protein fused to the N-terminal region of MinD-a spatial determinant of E. coli division plane assembly-in spheroplasts and observed its colocalization with CL to regions of large, negative membrane curvature. Interestingly, the distribution of MinD was similar in spheroplasts derived from a CL synthase knockout strain. These studies demonstrate the curvature dependence of CL in membranes and test whether these structures participate in the localization of MinD to regions of negative curvature in cells.A central question in cell biology is how the spatial organization of proteins and lipids is established, maintained, and replicated and how it fluctuates in response to external stimuli. Eukaryotic cells use several mechanisms to accomplish this task, including a dynamic cytoskeleton that controls the spatial and temporal position of proteins, nucleic acid, and organelles (1). The formation of lipid microdomains in the membrane also is involved in the localization of integral membrane proteins (2). These mechanisms play a critical role in cell physiology and behavior.Bacteria also use mechanisms for controlling the intracellular location of proteins, lipids, and nucleic acid. The persistent historical view of bacterial cells as lacking spatial control over their intracellular components inhibited the field. Bacteria are sophisticated organisms that use tightly regulated physiological mechanisms similar to many of those used by eukaryotic cells, including controlling shape, regulating growth and division, transporting intracellular components (e.g., proteins, plasmids, DNA, and RNA), and polarizing the cell (3, 4). These organisms have several remarkable structural characteristics, but one of the most fundamental questions in this area of microbiology-how cells produce, maintain, and replicate their spatial organization-still...

“…Differences in membrane composition may be essential to recruit proteins essential for polar growth. For example, in Bacillus subtilis, helical lipid domains guide the helical localization of MinD (19), and polar localization of DivIVA may be mediated by physical cues in the geometry and shape of the membrane (20). Reduced FM 4-64 signal has also been reported for the division site of E. coli, an area of active PG synthesis (21).…”

Section: Discussionmentioning

confidence: 99%

Dynamic FtsA and FtsZ localization and outer membrane alterations during polar growth and cell division in Agrobacterium tumefaciens

Zupan

Cameron

Anderson-Furgeson

et al. 2013

Growth and cell division in rod-shaped bacteria have been primarily studied in species that grow predominantly by peptidoglycan (PG) synthesis along the length of the cell. Rhizobiales species, however, predominantly grow by PG synthesis at a single pole. Here we characterize the dynamic localization of several Agrobacterium tumefaciens components during the cell cycle. First, the lipophilic dye FM 4-64 predominantly stains the outer membranes of old poles versus growing poles. In cells about to divide, however, both poles are equally labeled with FM 4-64, but the constriction site is not. Second, the cell-division protein FtsA alternates from unipolar foci in the shortest cells to unipolar and midcell localization in cells of intermediate length, to strictly midcell localization in the longest cells undergoing septation. Third, the cell division protein FtsZ localizes in a cell-cycle pattern similar to, but more complex than, FtsA. Finally, because PG synthesis is spatially and temporally regulated during the cell cycle, we treated cells with sublethal concentrations of carbenicillin (Cb) to assess the role of penicillin-binding proteins in growth and cell division. Cb-treated cells formed midcell circumferential bulges, suggesting that interrupted PG synthesis destabilizes the septum. Midcell bulges contained bands or foci of FtsA-GFP and FtsZ-GFP and no FM 4-64 label, as in untreated cells. There were no abnormal morphologies at the growth poles in Cb-treated cells, suggesting unipolar growth uses Cb-insensitive PG synthesis enzymes.agrobacterium cell cycle | bacterial cell growth | bacterial cell division | peptidoglycan synthesis