RESUMO
The common gonadotrophic hormone α-subunit (GTHα) has been previously isolated by our research group from A. gigas pituitaries; in the present work the cDNA sequences encoding FSHß and LHß subunits have also been isolated from the same species of fish. The FSH ß-subunit consists of 126 amino acids with a putative 18 amino acid signal peptide and a 108 amino acid mature peptide, while the LH ß-subunit consists of 141 amino acids with a putative 24 amino acid amino acid signal peptide and a 117 amino acid mature peptide. The highest identity, based on the amino acid sequences, was found with the order of Anguilliformes (61%) for FSHß and of Cypriniformes (76%) for LHß, followed by Siluriformes, 53% for FSHß and 75% for LHß. Interestingly, the identity with the corresponding human amino acid sequences was still remarkable: 45.1% for FSHß and 51.4% for LHß. Three dimensional models of ag-FSH and ag-LH, generated by using the crystal structures of h-FSH and h-LH as the respective templates and carried out via comparative modeling and molecular dynamics simulations, suggested the presence of the so-called "seat-belt", favored by a disulfide bond formed between the 3rd and 12th cysteine in both ß-subunits. The sequences found will be used for the biotechnological synthesis of A. gigas gonadotrophic hormones (ag-FSH and ag-LH). In a first approach, to ascertain that the cloned transcripts allow the expression of the heterodimeric hormones, ag-FSH has been synthesized in human embryonic kidney 293 (HEK293) cells, preliminarily purified and characterized.
