Comparative biochemical characterization of pufferfish saxitoxin and tetrodotoxin-binding protein (PSTBP) homologs in the plasma from four Takifugu species: Conservation of heat-stable PSTBP orthologs having three and two tandemly repeated lipocalin domains in genus Takifugu

To study the relationship between domain characteristics of pufferfish saxitoxin and tetrodotoxin binding protein (PSTBP) proteoforms and their thermal stability, a comparative biochemical characterization of PSTBPs from the plasma of four Takifugu species (T. flavipterus, T. pardalis, T. alboplumbeus and T. rubripes) was conducted by Western blot analysis. The heat-tolerance tetrodotoxin (TTX)-binding ability of PSTBP proteoforms in T. rubripes plasma was verified by ultrafiltration and liquid chromatography tandem mass spectrometry (LC-MS/MS). These results suggest that the heat-stable PSTBP proteoforms, composed of three and two tandemly repeated lipocalin domains, are genetically conserved and ubiquitous in the genus Takifugu. This study builds on our knowledge of the structural and functional properties of PSTBP proteoforms, which is vital for understanding how toxins are transmitted and accumulate in organisms and is essential for evaluating the potential risks of toxins in seafood.