Submitted to: Journal of Endocrinology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/9/1997
Publication Date: N/A
Citation: Interpretive Summary: The three pituitary glycoprotein hormones (FSH, LH and TSH) consist of a common alpha subunit for each species studied, combined with a beta subunit unique for each hormone. The relationship of these subunits was compared as nucleotide sequences and as amino acid sequences across a broad range of animal species, and from this comparison, the evolutionary distance was determined. Based on these analyses, five amino acids were conserved across all alpha and all beta subunits plus eight additional amino acids were conserved across all the beta subunits. Because these amino acids are conserved across all species examined, we expect these to play a significant role in protein structure and function, and they become obvious candidates for future research into protein structure.
Technical Abstract: On the basis of nucleotide sequences of the coding region and their predicted amino acid sequences, 58 glycoprotein hormone subunit genes were compared, aligned and used to construct phylogenetic trees for this family of anterior pituitary hormones. It included 17 alpha, 8 TSH beta, 6 FSH beta, 17 LH beta/CG beta, 4 fish gonadotropin (GTH)-I beta, 5 fish GTH-II beta and 1 additional fish GTH beta subunits. The reliability of the phylogenetic trees was probed with the bootstrapping test. Our results indicated that: 1) both the alpha- and beta-subunits of the family diverged from a common ancestral gene at about 927 million years ago; 2) FSH beta is more related to TSH beta than to LH beta; 3) bony fish GTH-I beta is highly related to mammalian FSH beta while the bony fish GTH-II beta is more related to mammalian LH beta. For scientific consistency and convenience, we propose the following nomenclature; all sub-mammalian type I gonadotropins be classified as FSH-like and type IIs be classified as LH-like hormones. Additionally, based on the results from this and other studies, an evolutionary scenario about this glycoprotein hormone family was proposed.