A tachylectin and a pore-forming MACPF protein combined into a snail egg neurotoxin

SANTIAGO ITUARTE; HORACIO HERAS; MATÍAS L. GIGLIO; JIAN-WEN QIU; HUAWEI MU

Córdoba

Congreso; LII Reunión Anual de la SAIB; 2016

Pomacea is a group of snails with aerial oviposition where adult females lay conspicuously colored egg masses that are ignored by most predators, which is associated to the presence of multifunctional proteins with defensive properties. Among them is the neurotoxin PcPV2 present in the eggs of P. canaliculata. A structurally similar protein (PmPV2) also with neurotoxic properties was recently found in the eggs of the sympatric species P. maculata. The aim of the present work was to determine the molecular and functional features of PmPV2. PmPV2 is composed by two subunits of ≈30 and ≈68 kDa. Full cDNA sequencing and analysis of the 30-kDa subunit show it is related to the tachylectin family of lectins. Its structure predicted by in silico modelling consists of a six-bladed beta propeller, a common arrangement in this family. Besides, PmPV2 showed agglutinating activity on rabbit erythrocytes. The 68-kDa subunit belongs to the MACPF family, particularly related to C8 and perforins from mammalian immune system. The predicted structure of this subunit presents the characteristic MACPF domains, including the transmembrane helixes (TMH) related to the insertion of the protein into the membrane. PmPV2 exhibit the ―AB toxin‖ structure found in bacterial attack and plant defensive toxins and restricted to PcPV2 in animals, composed of a delivery lectin covalently linked to a toxin (MACPF).