Hemoglobinas de Leptodactylus vastus: um modelo para entender a base molecular de adaptações funcionais em hemoglobinas de anfíbios

Abstract

The northwestern pepper-frog Leptodactylus vastus is an amphibian of semiaquatic habits endemic from the Brazilian northwest. We found that the red blood cells from this specie possess three isoforms of hemoglobin with different isoelectric points, which form disulfide bounds in vitro. SDS-PAGE shown two chains of relative molecular mass of 13.5 and 14.6 kDa, approximately. The oxygen dissociation curve for the pool of hemoglobins stripped of ions and allosteric effectors present high affinity (Kd = 4.5 μM) and low cooperativity (nH = 1.24). We observed the predominance of α-helices and elevated thermostability (Tm = 75 °C) by circular dichroism, that may be a consequence of disulfide bound formation in vitro. Revising the literature about amphibian hemoglobins, we propose that use L. vastus like a model for structural investigations may contribute to the understanding about how works the functional adaptations of this protein family in ectothermic vertebrates.