Scalarin (PsSC) is the most abundant perivitellin of the

perivitelline fluid The perivitelline fluid is an extracellular fluid found in the eggs of most gastropods and constitutes the main source of nutrition and defense for their embryos. It replaces the egg yolk of other animals, which in snail eggs is reduced to non-nutri ...

from ''

Pomacea scalaris ''Pomacea scalaris'' is a species of freshwater snail of the Ampullariidae (common name "apple snail") family, described by Alcide d'Orbigny Alcide Charles Victor Marie Dessalines d'Orbigny (6 September 1802 – 30 June 1857) was a French na ...

'' eggs. This glyco-lipo-caroteno protein is an approx. 380 kDa multimer combining multiple copies of six different 24-35 kDa subunits. As part of the petivitelline fluid, PsSC is probably playing a role as a nutrient source for the developing embryo in ''Pomacea scalaris'' eggs. As its orthologous ovorubin and PmPV1, this protein carries and stabilizes

carotenoid Carotenoids (), also called tetraterpenoids, are yellow, orange, and red organic compound, organic pigments that are produced by plants and algae, as well as several bacteria, and Fungus, fungi. Carotenoids give the characteristic color to pumpki ...

pigments. As a consequence, this perivitellin absorbs light throughout the visible range, a characteristic related to a photoprotective role in these aerially deposited eggs. The presence on its structure of

pigments is also associated with protective

antioxidative Antioxidants are Chemical compound, compounds that inhibit Redox, oxidation, a chemical reaction that can produce Radical (chemistry), free radicals. This can lead to polymerization and other chain reactions. They are frequently added to indust ...

properties. Like most other studied

perivitellins Perivitellins are egg proteins found in the perivitelline fluid of many gastropods. They are multifunctional complexes providing the developing embryo with nutrition, protection from the environment, and defense against predators. Despite the cent ...

from ''

Pomacea ''Pomacea'' is a genus of freshwater snails with gills and an operculum, aquatic gastropod mollusks in the family Ampullariidae, the apple snails. The genus is native to the Americas; most species in this genus are restricted to South America. ...

'' snails, PsSC is highly stable in a wide range of pH values and withstands gastrointestinal digestion, characteristics associated with an antinutritive defense system that deters predation by lowering the nutritional value of the eggs. Unlike ovorubin and PmPV1, PsSC is an active, strong

lectin Lectins are carbohydrate-binding proteins that are highly specific for sugar groups that are part of other molecules, so cause agglutination of particular cells or precipitation of glycoconjugates and polysaccharides. Lectins have a role in rec ...

, recognizing glycosphingolipids (notably, the

ganglioside A ganglioside is a molecule composed of a glycosphingolipid (ceramide and oligosaccharide) with one or more sialic acids (e.g. ''N''-acetylneuraminic acid, NANA) linked on the sugar chain. NeuNAc, an acetylated derivative of the carbohydrate sia ...

s GD1b, GT1b, and GD1a) and AB0 group antigens. Due to this activity, PsSC agglutinates

red blood cell Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...

s (notably those from rabbits and human A and B groups) as well as Gram-negative bacteria, indicating a putative immune role of this perivitellin. PsSC also binds to intestinal cells in culture and, when ingested, alters the morphophysiology of rat intestinal mucosa increasing its absorptive surface by elongating and narrowing villi, further supporting its role in a defense system against predation.

References

Proteins {{protein-stub