Abstract
Apple snail perivitellins are emerging as ecologically important reproductive proteins. To elucidate if the protective functions of the egg proteins of Pomacea canaliculata (Caenogastropoda, Ampullariidae), involved in embryo defenses, are present in other Pomacea species we studied scalarin (PsSC), the major perivitellin of Pomacea scalaris. Using small angle X-ray scattering, fluorescence and absorption spectroscopy and biochemical methods, we analyzed PsSC structural stability, agglutinating activity, sugar specificity and protease resistance. PsSC aggluttinated rabbit, and, to a lesser extent, human B and A erythrocytes independently of divalent metals Ca2+ and Mg2+ were strongly inhibited by galactosamine and glucosamine. The protein was structurally stable between pH 2.0 to 10.0, though agglutination occurred only between pH 4.0 to 8.0 (maximum activity at pH 7.0). The agglutinating activity was conserved up to 60°C and completely lost above 80°C, in agreement with the structural thermal stability of the protein (up to 60°C). PsSC was able to withstand in vitro gastrointestinal digestion, and showed no trypsin inhibition activity. The presence of lectin activity has been reported in eggs of other Pomacea snails, but here we link for the first time, this activity to an apple snail multifunctional perivitellin. This novel role for a snail egg storage protein is different from closely related P.canaliculata defensive proteins.
Highlights
Egg proteins of Pomacea are of particular interest since their functions seem to be related to the peculiar developmental environment of the embryos [1]
In an attempt to determine if the protective functions reported in perivitellins of other species of Pomacea are present in P. scalaris perivitellins, in the present paper we study the trypsin inhibition capacity, agglutinating activity, and sugar specificity as well as the structural stability against temperature and pH of Pomacea species we studied scalarin (PsSC)
Effect of pH on PsSC Structural Stability The structural stability of PsSC at different pH values was evaluated by fluorescence spectroscopy, absorbance spectroscopy and small angle X-ray scattering (SAXS)
Summary
Egg proteins of Pomacea are of particular interest since their functions seem to be related to the peculiar developmental environment of the embryos [1]. Studies on Pomacea canaliculata eggs showed that their major perivitellins, ovorubin (PcOvo) and PcPV2, play important roles in coping with these stressors [6]. Both perivitellins are structurally stable at high temperatures, being PcOvo stable at extreme pH values [7;8;9]. The major perivitellin of Pomacea scalaris eggs, scalarin (hereafter PsSC), was studied This protein is a 380 KDa oligomer composed by three subunits of 35, 28 and 24 KDa, noncovalently bound. PsSC shares structural features with PcOvo such as apoprotein composition, a high degree of glycosylation, and its prosthetic group [14]; the role of PsSC in embryo defenses was unknown
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