Ovorubin (PcOvo or PcPV1) is the most abundant perivitellin (>60 % total

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

) 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 canaliculata ''Pomacea canaliculata'', commonly known as the golden apple snail or the channeled apple snail, is a species of large freshwater snail with gills and an operculum, an aquatic gastropod mollusc in the family Ampullariidae, the apple snails. S ...

'' snail eggs. This glyco-lipo-caroteno protein complex is a approx. 300 kDa multimer of a combination of multiple copies of six different ~30 kDa subunits. Together with the other

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 ...

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'' eggs, ovorubin serves a nutrient source for developing embryos, notably to the intermediate and late stages. Moreover, after hatching, the protein is still detected in the lumen of the digestive gland ready to be endocytosed, therefore, acting as a nutrient source for the newly hatched snail. Ovorubin contains

carbohydrates A carbohydrate () is a biomolecule composed of carbon (C), hydrogen (H), and oxygen (O) atoms. The typical hydrogen-to-oxygen atomic ratio is 2:1, analogous to that of water, and is represented by the empirical formula (where ''m'' and ''n'' ma ...

and

carotenoid Carotenoids () are yellow, orange, and red organic pigments that are produced by plants and algae, as well as several bacteria, archaea, and fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, corn, tomatoes, cana ...

pigments as main

prosthetic groups A prosthetic group is the non-amino acid component that is part of the structure of the heteroproteins or conjugated proteins, being tightly linked to the apoprotein. Not to be confused with the cosubstrate that binds to the enzyme apoenzyme (e ...

, which are related to many physiological roles on ''

Pomacea ''Pomacea'' is a genus of freshwater snails with gills and an Operculum (gastropod), operculum, Aquatic animal, aquatic gastropod mollusks in the family Ampullariidae, the apple snails. The genus is native to the Americas; most species in this ge ...

'' aerial egg-laying strategy. Given that carbohydrates tend to retain water, the high glycosylation of ovorubin (~17 % w/w) was proposed as an embryo defense against water loss. The

pigments stabilized by ovorubin also provide the eggs of

antioxidant Antioxidants are Chemical compound, compounds that inhibit Redox, oxidation, a chemical reaction that can produce Radical (chemistry), free radicals. Autoxidation leads to degradation of organic compounds, including living matter. Antioxidants ...

and photoprotective capacities, crucial roles to cope with the harsh conditions of the aerial environment. The presence of carotenoid pigments is also responsible for the brightly reddish coloration of Ovorubin, and therefore snail eggs, which was related to a warning coloration (

aposematism Aposematism is the Advertising in biology, advertising by an animal, whether terrestrial or marine, to potential predation, predators that it is not worth attacking or eating. This unprofitability may consist of any defenses which make the pr ...

) advertising predators about the presence of deterrents. In fact, field evidence of egg unpalatability is provided by the fact that most animals foraging in habitats where the apple snails live ignore these eggs. Like most other studied

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'' snails, ovorubin 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.

References

{{reflist Proteins