PROSITE documentation PDOC00623

Glycoprotein hormones alpha chain signatures and profile

Glycoprotein hormones [1,2] (or gonadotropins) are a family of proteins which include the mammalian hormones follitropin (FSH), lutropin (LSH), thyrotropin (TSH) and chorionic gonadotropin (CG), as well as at least two forms of fish gonadotropins. All these hormones consist of two glycosylated chains (α and β). In mammalian gonadotropins, the α chain is identical in the four types of hormones but the β chains, while homologous, are different.

The α chains are highly conserved proteins of about 100 amino acid residues which contain ten conserved cysteines all involved in disulfide bonds [3], as shown in the following schematic representation.

                        +---------------------------+
            +----------+|             +-------------|--+
            |        **||***          |             |  |
        xxxxCxCxxxxxxCxCCxxxxxxxxxxxxxCCxxxxxxxxxxCxCxxCx
              |      |                 |         *|******
              +------|-----------------+          |
                     |                            |
                     +----------------------------+

'C': conserved cysteine involved in a disulfide bond.
'*': position of the patterns.

We have developed two patterns for these hormones. Each of them contains three of the conserved cysteines. We also developed a profile including the two regions covered by the patterns.