Prescient Hormone Receptor Evolution?

Science's STKE  11 Apr 2006:
Vol. 2006, Issue 330, pp. tw123
DOI: 10.1126/stke.3302006tw123

Highly integrated biological systems can provide a challenge in terms of understanding how such systems arose during the course of evolution. One such system involves the mineralocorticoid receptor (MR) and glucocorticoid receptor (GR), which arose from a gene duplication deep in the vertebrate lineage. MR binds to and is activated by the hormone aldosterone, which only appeared much later, in the lineage leading to tetrapods, raising the question of how each component "anticipated" the presence of the other. Bridgham et al. (see the Perspective by Adami) analyze the evolution of this system by reconstructing the ancestral corticoid receptor (AncCR) that gave rise to MR and GR and show that it already had substantial affinity for aldosterone as a consequence of its affinity for other more ancient hormones, possibly including 11-deoxycorticosterone. Furthermore, two single-nucleotide mutations in the AncCR yield a GR-like receptor with present-day low affinity for aldosterone.

J. T. Bridgham, S. M. Carroll, J. W. Thornton, Evolution of hormone-receptor complexity by molecular exploitation. Science 312, 97-101 (2006). [Abstract] [Full Text]

C. Adami, Reducible complexity. Science 312, 61-63 (2006). [Summary] [Full Text]