CONICET | Buscador de Institutos y Recursos Humanos

Freshwater snails of the genus Pomacea have among Ampullarids a tendency to increase their amphibious habits. Thus, Pomacea lays calcareous and brightly pigmented egg clutches on vegetation or other surfaces above the water. This exposes eggs to fluctuant temperatures and air desiccation. The conspicuous pigmentation is provided by high glycosilated oligomeric carotenoproteins possessing mainly astaxanthin carotenoids. It has been suggested that egg carotenoproteins play several roles in egg defenses and homoeostasis. The carotenoprotein PmPV1 is the main contributor of Pomacea maculata egg color. A recent biochemical characterization showed a great biochemical similarity with other carotenoproteins studied in other members of the genus (namely, P. canaliculata and P. scalaris). Here we report the first study on the structural stability of PmPV1 protein in relation to gastrointestinal digestion, pH, temperature, different chaotrops. In addition, further structural and functional studies are reported. Using two-dimensional electrophoresis we determined that glycosilation was not the only PmPV1 postranslational modification. Structural stability was analyzed by fluorescence and absorption spectroscopy assays. PmPV1 was structurally stable between pH 2.0 to pH 12.0, although some alteration of the fine structure in the visible region was observed at pH 2. The structural thermal stability of the protein was recorded from 25 °C up to 85 °C. No denaturalization throughout the temperature range neither alteration in its electrophoretic behavior after boiling PmPV1 10 min were observed. The protein is extremely resistant to digestion at enzyme concentrations that completely digest other proteins. No agglutinating and protease inhibitor activities were found in PmPV1. As a whole, these results show remarkable similarities and differences with the only other mollusk carotenoprotein so far studied: PcOvo and PsSC, from P. canaliculata and P. scalaris respectively. These comparisons further highlight the importance of these perivitellins in the reproductive strategy of Pomacea, increasing the scarce knowledge on the role of egg perivitelline fluid proteins on the reproductive strategies of mollusks.