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. 2007 Feb;189(3):801-6.
doi: 10.1128/JB.01549-06. Epub 2006 Dec 1.

Anionic lipids enriched at the ExPortal of Streptococcus pyogenes

Jason W Rosch  1 , Fong Fu Hsu, Michael G Caparon
Affiliations

Anionic lipids enriched at the ExPortal of Streptococcus pyogenes

"V体育平台登录" Jason W Rosch et al. J Bacteriol. 2007 Feb.

Abstract

The ExPortal of Streptococcus pyogenes is a membrane microdomain dedicated to the secretion and folding of proteins. We investigated the lipid composition of the ExPortal by examining the distribution of anionic membrane phospholipids VSports手机版. Staining with 10-N-nonyl-acridine orange revealed a single microdomain enriched with an anionic phospholipid whose staining characteristics and behavior in a cardiolipin-deficient mutant were characteristic of phosphatidylglycerol. Furthermore, the location of the microdomain corresponded to the site of active protein secretion at the ExPortal. These results indicate that the ExPortal is an asymmetric lipid microdomain, whose enriched content of anionic phospholipids may play an important role in ExPortal organization and protein trafficking. .

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Figures

FIG. 1.
FIG. 1.
S. pyogenes concentrates anionic phospholipids at discrete microdomains. Various bacterial species were stained with NAO and examined by fluorescence microscopy as described in Materials and Methods. Species included WT S. pyogenes (several representative images are shown in panels A1 to A6), E. coli (panel B), and B. subtilis (panels C1 and C2). Images presented were captured using the green fluorescent protein filter set and are shown in grayscale. WT S. pyogenes was also stained with Nile red (panel D). The bar in each panel is equivalent to 0.5 μm.
FIG. 2.
FIG. 2.
Lipid profile of streptococcal membranes. The electrospray ionization/mass spectrometry spectra of the lipid extracts arising from the [M-H]− ions of cardiolipin from Cls− cells (panel A) and from the WT (panel B). Panels C and D show the [M-H]− ions of phosphatidylglycerol species from the extracts shown in panels A and B, respectively. Ions from the (12:0)4-cardiolipin internal standard seen at m/z 1239.8 (panels A and B) are [M-H]− ions, while the ions seen at m/z 619.7 (panels C and D) are [M-2H]2− ions. Both the [M-H]− (panel A) and [M-2H]2− (panel C) ions of cardiolipin are absent in the lipid extract from Cls− cells but are abundant in the lipid extract from WT cells (panels B and D). In contrast, phosphatidyl glycerol is abundant from Cls− cells (panel C) and is of relatively low abundance in the WT (panel D).
FIG. 3.
FIG. 3.
The ExPortal is enriched in anionic lipids. WT S. pyogenes was stained with NAO and then examined in an assay which visualized the ExPortal as the site of secretion of active SpeB protease (33), as described in Materials and Methods. Cells were analyzed by fluorescence microscopy and examined for NAO staining and protease localization, as indicated. An overlay of NAO and protease images is shown on the right (Merge). Three representative groups of streptococcal cells, which are presented at various magnifications, are shown. Bars in leftmost panels are equivalent to 0.5 μm.
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References

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