RT-PCR- and MALDI-TOF mass spectrometry-based identification and discrimination of isoforms homologous to pufferfish saxitoxin- and tetrodotoxin-binding protein in the plasma of non-toxic cultured pufferfish (Takifugu rubripes).

Four genes of Takifugu rubripes, tentatively designated Tr1-Tr4, encoding homologs of pufferfish saxitoxin- and tetrodotoxin-binding protein, were identified by BLAST search and 3'-RACE. RT-PCR and MALDI-TOF mass spectrometry allowed the identification and discrimination of Tr isoforms from the non-toxically cultured specimens. The expression of Tr1 and Tr3 mRNAs exclusively in the liver and the presence of their products as 120-kDa plasma proteins were confirmed.