Ovorubin

Ovorubin (PcOvo or PcPV1) is the most abundant perivitellin (>60 % total protein) of the perivitelline fluid from Pomacea canaliculata snail eggs. This glyco-lipo-caroteno protein complex is a approximately 300 kDa multimer of different ~30 kDa subunits.^[1] The three-dimensional structure of ovorubin was determined by cryo-electron microscopy.^[2] The protein is decameric (10-mer) consisting of two copies of PcOvo1-5.

Together with the other perivitellins from Pomacea canaliculata eggs, ovorubin serves a nutrient source for developing embryos, notably to the intermediate and late stages.^[3] 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.^[3]

Ovorubin contains carbohydrates and carotenoid pigments as main prosthetic groups,^[4] which are related to many physiological roles on Pomacea 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.^[4] The carotenoid pigments stabilized by ovorubin also provide the eggs of antioxidant and photoprotective capacities, crucial roles to cope with the harsh conditions of the aerial environment.^{[3][5][6][7][8][excessive citations]} 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) advertising predators about the presence of deterrents.^[9][10] 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.^[11]

Like most other studied perivitellins from Pomacea 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.^[12][13]