Selective ligand-binding determinants in catfish and human gonadotropin receptors.

In mammals, the specificity of FSH-FSH receptor (FSHR), LH-LH receptor (LHR) and TSH-TSH receptor couples is such that no cross-activation occurs under normal physiological conditions. The interactions between fish gonadotropins and their receptors, however, appear to be less discriminatory. For example, the catfish FSHR is highly responsive to both catfish LH and catfish FSH, while the catfish LHR is specific for its cognate LH. Comparative structure-function studies aimed at elucidating the molecular basis of ligand promiscuity (in fish) and ligand selectivity (in mammals) are described in this paper.