Molecular cloning of follicle-stimulating hormone (FSH)-β subunit cDNA from duck pituitary

We have cloned FSH-β cDNA from duck pituitary gland by reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA end (RACE) methods. The cloned duck FSH-β cDNA contains 1909-bp nucleotides including 396-bp of open-reading frame and 1491-bp of 3′-untranslational region. The open-reading frame encodes a 131-amino acid protein with a putative 20-amino acid signal peptide and a putative 111-amino acid mature protein. The deduced amino acid sequence shows a remarkable similarity (94–98%) to those of other avian FSH-β subunits; while it exhibits lower similarities with those of turtles (82–84%), mammals (63–71%), and amphibians (53–57%). The structural model analysis of duck FSH suggests that the cysteine-knot and β-strands for maintaining the specific structural frame, and the “seat-belt” loop for specific binding to FSH receptor have been conserved in tetrapodian FSH-βs.