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Figure 5 | Biology Direct

Figure 5

From: CREST - a large and diverse superfamily of putative transmembrane hydrolases

Figure 5

The topology and subcellular localization of four CREST proteins. Like in Figure 4a, TM7 is set as neighboring to TM2 and TM3 to reflect possible spatial closeness between TM2, TM3 and TM7. Putative active site locations are marked by six-point stars. Alkaline ceramidases and Per1/PGAP3 are located in the ER or the Golgi membrane with their C-termini in the cytosol. Alkaline ceramidases catalyze the hydrolysis of ceramide to sphingosine. Per1/PGAP3 is required for phospholipase A2 activity that removes one of the two fatty acid chains (shown in zigzagged shapes) from the GPI-anchored protein (labeled 'G-A-P'). The chemical structures of ceramide and the GPI-anchored protein are shown (R1 and R2 are two aliphatic chains; P, I and S in circles represent phosphate group, inositol group, and suger or other groups connecting to the protein, respectively). The amide bond in ceramide hydrolyzed by alkaline ceramidase and the ester bond in the GPI-anchored protein hydrolyzed by Per1/PGAP3 are indicated by downward arrows. Adiponectin receptors and SID-1 are located in the plasma membrane with their N-termini in the cytosol. Adiponectin receptors interact with the extracellular hormone adiponectin (shown as a triangle) and may possess ceramidase or other hydrolase activity (marked by a dotted arrow). The putative dsRNA transporter SID-1 may possess an unknown hydrolase activity (marked by a question mark).

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