Reconstituting an Ancient Hormone Receptor

Can the ancestors of present-day proteins be reconstructed to determine what kinds of functionality they might have had? Thornton et al. have examined a class of steroid hormone receptor proteins previously believed to be restricted to vertebrates. An estrogen receptor gene from a mollusk was identified and characterized, suggesting that this family of proteins in fact predates the origin of bilaterally symmetrical animals. Using phylogenic approaches, the hypothesized 670 to 1100 million years old ancestor (Proterozoic) protein was then reconstructed, synthesized, and expressed. The primordial steroid receptor was likely to have been an estrogen-activated protein. J. W. Thornton, E. Need, D. Crews, Resurrecting the ancestral steroid receptor: Ancient origin of estrogen signaling. Science 301 , 1714-1717 (2003). [Abstract] [Full Text]