Molecular and Cellular Aspects of Chitin Synthesis in Larval Artemia
The cuticle of Artemia and other crustaceans contains chitin which is covalently attached to protein[1–3]. While the role of such proteins in structural support of the cuticle seems clear, the possible functions of the proteins in the biosynthesis of the cuticle are not obvious. Recent work in my laboratory has indicated that crustaceans synthesize a chitin oligosaccharide via a dolichol-linked intermediate. Subsequent transfer of the oligosaccharides to either endogenous polypeptides or synthetic peptide acceptors yields a chitoprotein which may serve as a substrate for chitin synthetase, the enzyme responsible for polymerization of macromolecular chitin. However, the pathway of synthesis for this material within the crustacean epithelial cell is not clear; one notion is that the chitoprotein is synthesized in the rough endoplasmic reticulum (RER), moves to the Golgi apparatus (where chitin synthetase is presumably located) and serves as a primer molecule for chitin synthetase, yielding a chitin-protein complex. The mechanism whereby this product is exported to the outside of the apical membrane and incorporated into the growing cuticle is not known.
KeywordsGolgi Apparatus Apical Membrane Colloidal Gold Electron Microscope Level Chitin Synthesis
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- 2.S. Hunt, “Protein Polysaccharide Complexes in Invertebrates,” Academic Press, New York (1970).Google Scholar
- 5.M. N. Horst, Glycosylation of exogenous peptide acceptors by larval brine shrimp microsomes, in: “UCLA Symposium on Synthetic Peptides: Approaches to Biological Problems,” Plenum Press, New York (in press).Google Scholar
- 6.M. N. Horst, The biosynthesis of crustacean chitin by a microsomal enzyme from larval brine shrimp, Biol. Chem. 256:1412 (1980).Google Scholar
- 13.M. N. Horst and R. M. Roberts, Solubilization, electrofocusing and two-dimensional electrophoresis of plasma membrane Polypeptides from Chinese hamster ovary cells, in: “Electrofocus/78” Elsevier, New York (1979).Google Scholar
- 16.A. Johnstone and R. Thorpe, “Immunochemistry in Practice,” Blackwell, Boston (1982).Google Scholar
- 19.J. Polak and I. Varndell, “Immunolabeling for Electron Microscopy,” Elsevier, New York (1984).Google Scholar
- 21.J. DeMey, Colloidal gold as a marker and tracer in light and electron microscopy, EMSA Bulletin 14:54 (1984).Google Scholar
- 22.P. Lewis and D. Knight, Staining methods for sectioned material, in: “Practical Methods for Electron Microscopy,” A. Glauert, ed., Elsevier, New York (1982).Google Scholar
- 24.M. Williams, Autoradiography and immunocytochemistry in: “Practical Methods in Electron Microscopy,” A. Glauert, ed., Elsevier, New York (1977).Google Scholar