Proteins of crustacean exoskeleton: III. Glycoproteins in the Bermuda land crab Gecarcinus lateralis
Document Type
Article
Publication Date
1-1-1995
Description
Chitin and protein are major components of crustacean exoskeletons. In insect cuticles, glycosylation is one of the predominant post‐translational modifications of the proteins. Investigations of glycosylation of crustacean exoskeletal proteins are much more limited. We have used lectins to follow changes in glycosylation of proteins in the exoskeletal layers of the Bermuda land crab Gecarcinus lateralis at selected stages of the intermolt cycle. Proteins extracted from the individual layers during anecdysis and late proecdysis as well as from the layers of exuviae were electrophoresed on sodium dodecyl sulfate (SDS)‐polyacrylamidegels, blotted to polyvinylidene difluoride membranes, and reacted with biotinylated lectins. Seven lectins were tested: concanavalin A (Con A), soybean agglutinin (SBA), wheat germ agglutinin (WGA), Dolichos biflorus agglutinin (DBA), Ulex europaeus agglutinin(UEA I), Ricinus communis agglutinin (RCA120), and peanut agglutinin (PNA). Con A, which binds primarily to mannose residues, produced the strongest signals. Duringanecdysis, most of the binding occurred with protein bands larger than 31 kDa, while in lateproecdysis and in layers from exuviae, small as well as large proteins were bound. N‐glycosidase F digestion of electrotransferred proteins and subsequent treatment with Con A indicated both N‐linked and O‐linked glycosylation. SBA, which binds to both α‐and β‐linked N‐acetylgalactosamine, was the second most reactive lectin, and the number of exoskeletal proteins to which it bound also increased in late proecdysis. Little or no binding of DBA, RCA120, or PNA, which react with α‐linked N‐acetylgalactosamine, indicated that the N‐acetylgalactosamine was β‐linked. The specificity of binding of Con A or SBA was demonstrated by inhibition with methyl‐α‐D‐mannopyranoside and N‐acetyl‐D‐galactosamine, respectively. Binding of UEAI revealed the presence of fucose residues on a few proteins. As the exoskeleton was degraded during proecdysis, protein bands that were not detected by lectin binding during anecdysis were modified in such a way that they became accessible to lectins.
Citation Information
Kumari, S. Sindhu; and Skinner, Dorothy M.. 1995. Proteins of crustacean exoskeleton: III. Glycoproteins in the Bermuda land crab Gecarcinus lateralis. Journal of Experimental Zoology. Vol.271(6). 413-424. https://doi.org/10.1002/jez.1402710602 ISSN: 0022-104X