Evolution of pituitary hormones

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We have cloned cDNAs encoding precursor molecules of luteinizing hormone (LH) beta subunits of the chicken and Japanese quail, the beta subunit of follicle-stimulating hormone of Japanese quail and alpha subunits of the Japanese quail, bullfrog, toad and Australian lung-fish. Using these data and data of other vertebrate species reported, we compared the primary structure of the molecules among vertebrate species. The primary structure of the alpha subunits was highly conserved and that of the beta subunits was less conserved. We also predicted the secondary sturctures of the alpha and beta subunits of these gonadotropins and thyrotropins. It was very well coincided among vertebrate species in both subunits. We concluded that the three dimensional structure is more highly conserved than the primary structure in vertebrates. We constructed a phylogenic tree of the beta subunits of gonadotropins and thyrotropin. It was found that follicle-stimulating hormone is more closely related to thyrotropin than luteinizing hormone. This is different from the classic grouping of members of the gonadotropin/thyrotropin family in which follicle-stimulating hormone and luteinizing hormone used to be categorized together as gonadotropin and thyrotropin was separated from gonadotropin. We also found that the alpha subunit of Australian lung-fish is more closely related to alpha subunits of tetrapod vertebrates than to those of teleosts. A similar result was obtained in neurohypophyseal hormone precursor molecules.