CONICET | Buscador de Institutos y Recursos Humanos

The evolution of structure-function relationship of hyperstableproteins is poorly understood. Studying Pomacea snail carotenoproteinsas a model, we observed that those involved in embryonutrition and defense have changed during genus evolution: whilebrightly colored ones of the most derived clade (P. canaliculata andP. maculata) act as antinutritive defenses against predators; thoseof P. scalaris, pale, additionally possess a strong lectin activity. Theaim of this work was to analyze the evolutionary trends of Pomaceacarotenoproteins, studying PpPV1, the carotenoprotein of P. patula,a basal member of the genus. PpPV1 absorption spectrum showsa 380 nm maximum indicating a blue-shift from the basal cladecompared with the derived species (430 ? 510 nm). Electrophoreticmobility also shifted from a mobility equivalent to a 450 kDa proteinin native PpPV1 towards lower MWs in the most derived carotenoproteins(293 ? 380 KDa). Despite these differences, PpPV1 havesimilar subunits MW to those of its derived species homologues. Derivedclades are kinetically stable (a high energetic barrier that notallow passing from native to denaturized state). This characteristicwas evaluated in PpPV1 hypothesizing that was acquired in derivativeclades in species with notable reproductive success. However,PpPV1 oligomer withstands boiling and is resistant to SDS-induceddenaturation, highlighting that carotenoproteins of Pomacea eggsare already thermal and kinetically stable in the most basal species.Functional analysis of hemagluttinating activity revealed thatP. patula periviteline fluid surrounding the embryo has a moderatelectin activity that is not mainly ascribed to PpPV1. In conclusion, thecomparative analysis shows that, while carotenoprotein color andsize changed, subunits and structural stability was conserved. Thelater may have increased tolerance to mutations that acceleratedthe evolution of new functions.

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