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Fig. 3 | BMC Biology

Fig. 3

From: Silicanin-1 is a conserved diatom membrane protein involved in silica biomineralization

Fig. 3

Localization of Sin1-GFP fusion proteins in T. pseudonana. a SEM images of biosilica from individual cells in two different orientations. b Live cells, biosilica, and biosilica-associated organic matrix from transformant strains expressing Sin1-GFPN or Sin1-GFPC. The fusion proteins were expressed under control of the endogenous Sin1 promoter and terminator sequences. The ‘Live cell’ panels show confocal fluorescence images (z-projection) of individual cells in girdle view (left panel, and third panel from the left) and in valve view (second panel from the left). Green color indicates the GFP fusion proteins and the red color is caused by chlorophyll autofluorescence. The biosilica and organic matrix panels show bright field microscopy images (BF) and the corresponding epifluorescence microscopy images (EF) of material isolated from Sin1-GFPN- or Sin1-GFPC-expressing transformants. Scale bars for all images: 2 μm. c Proposed intracellular proteolytic processing of Sin1. Sin1 becomes cleaved by a protease between the luminal domain (lum) and the transmembrane helix (orange). The luminal domain is incorporated into the biosilica, while the transmembrane helix and the cytosolic domain (blue squiggle) become degraded

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