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Figure 3. Electron micrographs of porcine secretory-stage enamel showing immunolocalization of enamelin at the enamel surface near the ameloblast Tomes’ process. The results from four affinity-purified anti-peptide antibodies are shown: (a) enamelin N-terminus (Dohi et al., 1998); (b) 32-kDa N-terminus (Uchida et al., 1991a); (c) 34-kDa N-terminus; and (d) enamelin C-terminus (Hu et al., 1997b). Below the histology is a diagram showing the different enamelin cleavage products and the positions of the sequences used to make antibodies. Pig enamelin has 1142 amino acids. The first 38 amino acids constitute the signal peptide. The secreted protein has an apparent molecular weight of 186 kDa (amino acids 39–1142); partially characterized enamelin cleavage products are the 155 kDa (39-unknown), 142 kDa (39 to unknown), 89 kDa (39 to 665), 32 kDa (174–279), 25 kDa (515–665), and the 34 kDa (670-unknown) (Fukae et al., 1996). Key: Tomes’ processes (TP), enamel matrix (E), secretory granules (SG), secretory face (SF), non-secretory face (NF) of Tomes’ process endoplasmic reticulum (ER), terminal web (TW), stippled material (SM). Bar = 1.0 µm.
