Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P02794 (ferritin)
 17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To ascertain the directionality of chitin synthesis by yeast plasma membranes, the external surface of Saccharomyces cerevisiae protoplasts was labeled with ferritin--concanavalin A. After protoplast lysis, plasma membranes were isolated and treated with trypsin to activate chitin synthase (UDP-2-acetamido-2-deoxy-D-glucose:chitin 4-beta-acetamidodeoxy-D-glucosyl-transferase, EC 2.4.1.16). The membranes were then enrobed in agar and allowed to synthesize chitin from UDP-N-acetylglucosamine. After fixation and embedding in Epon, thin sections were stained for chitin with wheat germ agglutinin--colloidal gold complexes. The chitin marker was found near the ferritin-labeled external face of the membrane--i.e., the polysaccharide was located on the outside of the membrane, as it is in the intact cell. Chitin synthase activity was not detected in intact protoplasts before or after treatment with trypsin. The enzyme became available to trypsin activation after lysis of the protoplasts. Together with similar, previously reported experiments on the inactivation of chitin synthase by glutaraldehyde, these results indicate that the enzyme faces the interior of the cell. We conclude that, both in vivo and in vitro, the synthase receives N-acetylglucosamine residues from UDP-N-acetylglucosamine at the cytoplasmic face of the membrane and transfers them vectorially to a growing chain of chitin that is concomitantly extruded to the outside.
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PMID:Vectorial synthesis of a polysaccharide by isolated plasma membranes. 622 77

The operculum is a novel structure in gastropod molluscs. Because the operculum shows notable similarities to the shell plate, we asked whether there were an evolutionary link between these two secretory organs. We found that some of the genes involved in shell-field development are expressed in the operculum, such as dpp and grainyhead, whereas engrailed and Hox1 are not. Specific knockdown of dpp by injection of double-stranded RNA (dsRNA) resulted in malformation of the shell plate. The shell plate was smaller due to failure of activation of cell proliferation in the shell-field margin. The expressions of grainyhead and chitin synthase 1 in the shell field margin were suppressed by dpp-dsRNA. However, matrix secretion was not completely abolished, and the expressions of ferritin, engrailed or Hox1 were not affected by dpp-dsRNA, indicating that dpp is partly involved in the developmental pathway for shell matrix secretion. We also present evidence that dpp performs a key role in operculum development. Indeed, dpp-dsRNA impaired matrix secretion in the operculum as well as expression of grainyhead. Based on these observations that dpp is important for development of both the shell plate and operculum, we conclude that co-option of dpp to the posterior part of the foot contributed to the innovation of the operculum in gastropods.
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PMID:Developmental role of dpp in the gastropod shell plate and co-option of the dpp signaling pathway in the evolution of the operculum. 2254 1